Engineered Fuel Feed Stock

ABSTRACT

Disclosed are novel engineered fuel feed stocks, feed stocks produced by the described processes, and methods of making the fuel feed stocks. Components derived from processed MSW waste streams can be used to make such feed stocks which are substantially free of glass, metals, grit and noncombustibles. These feed stocks are useful for a variety of purposes including as gasification and combustion fuels.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. 119(e)to co-pending U.S. application No. 61/076,025, filed on Jun. 26, 2008,and entitled “ENGINEERED FUEL PELLET,” and U.S. application No.61/076,020, filed Jun. 26, 2008, and entitled “ENGINEERED INERT FUELPELLET,” the disclosures of which are hereby incorporated by referencein their entireties.

FIELD OF THE INVENTION

The present invention relates to alternative fuels. In particular, theinvention relates to engineering engineered fuel feed stock suited forspecific applications including as a fossil fuel substitute forcombustion, as well as feed stock for gasification to produce highquality synthesis gas. Feed stock can be engineered to control airemission profiles upon combustion or gasification (such as dioxins,sulfur emitted, as well as others pollutants) as well as to avoidslagging. The feed stock described herein comprises at least onecomponent of processed municipal solid waste, and optionally othercomponents.

BACKGROUND OF THE INVENTION

Sources of fossil fuels useful for heating, transportation, and theproduction of chemicals as well as petrochemicals are becomingincreasingly more scarce and costly. Industries such as those producingenergy and petrochemicals are actively searching for cost effectiveengineered fuel feed stock alternatives for use in generating thoseproducts and many others. Additionally, due to the ever increasing costsof fossil fuels, transportation costs for moving engineered fuel feedstocks for production of energy and petrochemicals is rapidlyescalating.

These energy and petrochemical producing industries, and others, haverelied on the use of fossil fuels, such as coal and oil and natural gas,for use in combustion and gasification processes for the production ofenergy, for heating and electricity, and the generation of synthesis gasused for the downstream production of chemicals and liquid fuels, aswell as an energy source for turbines.

Combustion and gasification are thermochemical processes that are usedto release the energy stored within the fuel source. Combustion takesplace in a reactor in the presence of excess air, or excess oxygen.Combustion is generally used for generating steam which is used to powerturbines for producing electricity. However, the brute force nature ofthe combustion of fuel causes significant amounts of pollutants to begenerated in the gas produced. For example, combustion in an oxidizingatmosphere of, for example, fossil fuels such as coal, oil and naturalgas, releases nitrogen oxides, a precursor to ground level ozone whichcan stimulate asthma attacks. Combustion is also the largest source ofsulfur dioxide which in turn produces sulfates that are very fineparticulates. Fine particle pollution from U.S. power plants cuts shortthe lives of over 30,000 people each year. Hundreds of thousands ofAmericans suffer from asthma attacks, cardiac problems and upper andlower respiratory problems associated with fine particles from powerplants.

Gasification also takes place in a reactor, although in the absence ofair, or in the presence of substoichiometric amounts of oxygen. Thethermochemical reactions that take place in the absence of oxygen orunder substoichiometric amounts of oxygen do not result in the formationof nitrogen oxides or sulfur oxides. Therefore, gasification caneliminate much of the pollutants formed during the firing of fuel.

Gasification generates a gaseous, fuel rich product known as synthesisgas (syngas). During gasification, two processes take place that convertthe fuel source into a useable fuel gas. In the first stage, pyrolysisreleases the volatile components of the fuel at temperatures below 600°C. (1112° F.), a process known as devolatization. The pyrolysis alsoproduces char that consists mainly of carbon or charcoal and ash. In thesecond gasification stage, the carbon remaining after pyrolysis iseither reacted with steam, hydrogen, or pure oxygen. Gasification withpure oxygen results in a high quality mixture of carbon monoxide andhydrogen due to no dilution of nitrogen from air.

A variety of gasifier types have been developed. They can be groupedinto four major classifications: fixed-bed updraft, fixed-bed downdraft,bubbling fluidized-bed and circulating fluidized bed. Differentiation isbased on the means of supporting the fuel source in the reactor vessel,the direction of flow of both the fuel and oxidant, and the way heat issupplied to the reactor. The advantages and disadvantages of thesegasifier designs have been well documented in literature, for example,Rezaiyan, J. and Nicholas P. Cheremisinoff, Gasification Technology, APrimer for Engineers and Scientists. Boca Raton: CRC Press, 2005, thecontents of which are hereby incorporated by reference.

The updraft gasifier, also known as counterflow gasification, is theoldest and simplest form of gasifier; it is still used for coalgasification. The fuel is introduced at the top of the reactor, and agrate at the bottom of the reactor supports the reacting bed. Theoxidant in the form of air or oxygen and/or steam are introduced belowthe grate and flow up through the bed of fuel and char. Completecombustion of char takes place at the bottom of the bed, liberating CO₂and H₂O. These hot gases (˜1000° C.) pass through the bed above, wherethey are reduced to H₂ and CO and cooled to about 750° C. Continuing upthe reactor, the reducing gases (H₂ and CO) pyrolyse the descending dryfuel and finally dry any incoming wet fuel, leaving the reactor at a lowtemperature (˜500° C.). Updraft gasification is a simple, low costprocess that is able to handle fuel with a high moisture and highinorganic content. The primary disadvantage of updraft gasification isthat the synthesis-gas contains 10-20% tar by weight, requiringextensive syngas cleanup before engine, turbine or synthesisapplications.

Downdraft gasification, also known as concurrent-flow gasification, hasthe same mechanical configuration as the updraft gasifier except thatthe oxidant and product gases flow down the reactor, in the samedirection as the fuel, and can combust up to 99.9% of the tars formed.Low moisture fuel (<20%) and air or oxygen are ignited in the reactionzone at the top of the reactor, generating pyrolysis gas/vapor, whichburns intensely leaving 5 to 15% char and hot combustion gas. Thesegases flow downward and react with the char at 800 to 1200° C.,generating more CO and H₂ while being cooled to below 800° C. Finally,unconverted char and ash pass through the bottom of the grate and aresent to disposal. The advantages of downdraft gasification are that upto 99.9% of the tar formed is consumed, requiring minimal or no tarcleanup. Minerals remain with the char/ash, reducing the need for acyclone. The disadvantages of downdraft gasification are that itrequires feed drying to a low moisture content (<20%). The syngasexiting the reactor is at high temperature, requiring a secondary heatrecovery system; and 4-7% of the carbon remains unconverted.

The bubbling fluidized bed consists of fine, inert particles of sand oralumina, which have been selected for size, density, and thermalcharacteristics. As gas (oxygen, air or steam) is forced through theinert particles, a point is reached when the frictional force betweenthe particles and the gas counterbalances the weight of the solids. Atthis gas velocity (minimum fluidization), the solid particles becomesuspended, and bubbling and channeling of gas through the media mayoccur, such that the particles remain in the reactor and appear to be ina “boiling state”. The minimum fluidization velocity is not equal to theminimum bubbling velocity and channeling velocity. For coarse particles,the minimum bubbling velocity and channeling velocity are close oralmost equal, but the channeling velocity may be quite different, due tothe gas distribution problem. The fluidized particles tend to break upthe fuel fed to the bed and ensure good heat transfer throughout thereactor. The advantages of bubbling fluidized-bed gasification are thatit yields a uniform product gas and exhibits a nearly uniformtemperature distribution throughout the reactor. It is also able toaccept a wide range of fuel particle sizes, including fines; provideshigh rates of heat transfer between inert material, fuel and gas.

The circulating fluidized bed gasifiers operate at gas velocities higherthan the so-called transport velocity or onset velocity of circulatingfluidization at which the entrainment of the bed particles dramaticallyincreases so that continuous feeding or recycling back the entrainedparticles to the bed is required to maintain a stable gas-solid systemin the bed.—The circulating fluidized-bed gasification is suitable forrapid reactions offering high heat transport rates due to high heatcapacity of the bed material. High conversion rates are possible withlow tar and unconverted carbon.

Normally these gasifiers use a homogeneous source of fuel. A constantunchanging fuel source allows the gasifier to be calibrated toconsistently form the desired product. Each type of gasifier willoperate satisfactorily with respect to stability, gas quality,efficiency and pressure losses only within certain ranges of the fuelproperties. Some of the properties of fuel to consider are energycontent, moisture content, volatile matter, ash content and ash chemicalcomposition, reactivity, size and size distribution, bulk density, andcharring properties. Before choosing a gasifier for any individual fuelit is important to ensure that the fuel meets the requirements of thegasifier or that it can be treated to meet these requirements. Practicaltests are needed if the fuel has not previously been successfullygasified.

Normally, gasifiers use a homogeneous source of fuel for producingsynthesis gas. A constant unchanging fuel source allows the gasifier tobe calibrated to consistently form the desired product. Each type ofgasifier will operate satisfactorily with respect to stability, gasquality, efficiency and pressure losses only within certain ranges ofthe fuel properties. Some of the properties of fuel to consider forcombustion and gasification are high heating value (HHV) content, carbon(C), hydrogen (H), and oxygen (O) content, BTU value, moisture content,volatile matter content, ash content and ash chemical composition,sulfur content, chlorine content, reactivity, size and sizedistribution, and bulk density. Before choosing a gasifier for anyindividual fuel it is important to ensure that the fuel meets therequirements of the gasifier or that it can be treated to meet theserequirements. Practical tests are needed if the fuel has not previouslybeen successfully gasified.

One potential source for a large amount of feed stock for gasificationis waste. Waste, such as municipal solid waste (MSW), is typicallydisposed of or used in combustion processes to generate heat and/orsteam for use in turbines. The drawbacks accompanying combustion havebeen described above, and include the production of pollutants such asnitrogen oxides, sulfur oxide, particulates and products of chlorinethat damage the environment.

One of the most significant threats facing the environment today is therelease of pollutants and greenhouse gases (GHGs) into the atmospherethrough the combustion of fuels. GHGs such as carbon dioxide, methane,nitrous oxide, water vapor, carbon monoxide, nitrogen oxide, nitrogendioxide, and ozone, absorb heat from incoming solar radiation but do notallow long-wave radiation to reflect back into space. GHGs in theatmosphere result in the trapping of absorbed heat and warming of theearth's surface. In the U.S., GHG emissions come mostly from energy usedriven largely by economic growth, fuel used for electricity generation,and weather patterns affecting heating and cooling needs. Energy-relatedcarbon dioxide emissions, resulting from petroleum and natural gas,represent 82 percent of total U.S. human-made GHG emissions. Anothergreenhouse gas, methane, comes from landfills, coal mines, oil and gasoperations, and agriculture; it represents nine percent of totalemissions. Nitrous oxide (5 percent of total emissions), meanwhile, isemitted from burning fossil fuels and through the use of certainfertilizers and industrial processes. World carbon dioxide emissions areexpected to increase by 1.9 percent annually between 2001 and 2025. Muchof the increase in these emissions is expected to occur in thedeveloping world where emerging economies, such as China and India, fueleconomic development with fossil energy. Developing countries' emissionsare expected to grow above the world average at 2.7 percent annuallybetween 2001 and 2025; and surpass emissions of industrialized countriesnear 2018.

Waste landfills are also significant sources of GHG emissions, mostlybecause of methane released during decomposition of waste, such as, forexample, MSW. Compared with carbon dioxide, methane is twenty-timesstronger than carbon dioxide as a GHG, and landfills are responsible forabout 4% of the anthropogenic emissions. Considerable reductions inmethane emissions can be achieved by combustion of waste and bycollecting methane from landfills. The methane collected from thelandfill can either be used directly in energy production or flared off,i.e., eliminated through combustion without energy production(Combustion Of Waste May Reduce Greenhouse Gas Emissions, ScienceDaily,Dec. 8, 2007).

One measure of the impact human activities have on the environment interms of the amount of green house gases produced is the carbonfootprint, measured in units of carbon dioxide (CO₂). The carbonfootprint can be seen as the total amount of carbon dioxide and otherGHGs emitted over the full life cycle of a product or service. Normally,a carbon footprint is usually expressed as a CO₂ equivalent (usually inkilograms or tons), which accounts for the same global warming effectsof different GHGs. Carbon footprints can be calculated using a LifeCycle Assessment method, or can be restricted to the immediatelyattributable emissions from energy use of fossil fuels.

An alternative definition of carbon footprint is the total amount of CO₂attributable to the actions of an individual (mainly through theirenergy use) over a period of one year. This definition underlies thepersonal carbon calculators. The term owes its origins to the idea thata footprint is what has been left behind as a result of the individual'sactivities. Carbon footprints can either consider only direct emissions(typically from energy used in the home and in transport, includingtravel by cars, airplanes, rail and other public transport), or can alsoinclude indirect emissions which include CO₂ emissions as a result ofgoods and services consumed, along with the concomitant waste produced.

The carbon footprint can be efficiently and effectively reduced byapplying the following steps: (i) life cycle assessment to accuratelydetermine the current carbon footprint; (ii) identification of hot-spotsin terms of energy consumption and associated CO₂-emissions; (iii)optimization of energy efficiency and, thus, reduction of CO₂-emissionsand reduction of other GHG emissions contributed from productionprocesses; and (iv) identification of solutions to neutralize the CO₂emissions that cannot be eliminated by energy saving measures. The laststep includes carbon offsetting, and investment in projects that aim atthe reducing CO₂ emissions.

The purchase of carbon offsets is another way to reduce a carbonfootprint. One carbon offset represents the reduction of one ton ofCO₂-eq. Companies that sell carbon offsets invest in projects such asrenewable energy research, agricultural and landfill gas capture, andtree-planting.

Purchase and withdrawal of emissions trading credits also occur, whichcreates a connection between the voluntary and regulated carbon markets.Emissions trading schemes provide a financial incentive fororganizations and corporations to reduce their carbon footprint. Suchschemes exist under cap-and-trade systems, where the total carbonemissions for a particular country, region, or sector are capped at acertain value, and organizations are issued permits to emit a fractionof the total emissions. Organizations that emit less carbon than theiremission target can then sell their “excess” carbon emissions.

For many wastes, the disposed materials represent what is left overafter a long series of steps including: (i) extraction and processing ofraw materials; (ii) manufacture of products; (iii) transportation ofmaterials and products to markets; (iv) use by consumers; and (v) wastemanagement. At virtually every step along this “life cycle,” thepotential exists for greenhouse gas (GHG) impacts. Waste managementaffects GHGs by affecting energy consumption (specifically, combustionof fossil fuels) associated with making, transporting, using, anddisposing the product or material that becomes a waste and emissionsfrom the waste in landfills where the waste is disposed.

Incineration typically reduces the volume of the MSW by about 90% withthe remaining 10% of the volume of the original MSW still needing to belandfilled. This incineration process produces large quantities of theGHG CO₂. Typically, the amount of energy produced per equivalents CO₂expelled during incineration are very low, thus making incineration ofMSW for energy production one of the worst offenders in producing GHGreleased into the atmosphere. Therefore, if GHGs are to be avoided, newsolutions for the disposal of wastes, such as MSW, other thanlandfilling and incineration, are needed.

Each material disposed of as waste has a different GHG impact dependingon how it is made and disposed. The most important GHGs for wastemanagement options are carbon dioxide, methane, nitrous oxide, andperfluorocarbons. Of these, carbon dioxide (CO₂) is by far the mostcommon GHG emitted in the US. Most carbon dioxide emissions result fromenergy use, particularly fossil fuel combustion. Carbon dioxide is thereference gas for measurement of the heat-trapping potential (also knownas global warming potential or GWP). By definition, the GWP of onekilogram (kg) of carbon dioxide is 1. Methane has a GWP of 21, meaningthat one kg of methane has the same heat-trapping potential as 21 kg ofCO₂. Nitrous oxide has a GWP of 310. Perfluorocarbons are the mostpotent GHGs with GWPs of 6,500 for CF₄ and 9,200 for C₂F₆. Emissions ofcarbon dioxide, methane, nitrous oxide, and perfluorocarbons are usuallyexpressed in “carbon equivalents.” Because CO₂ is 12/44 carbon byweight, one metric ton of CO₂ is equal to 12/44 or 0.27 metric tons ofcarbon equivalent (MTCE). The MTCE value for one metric ton of each ofthe other gases is determined by multiplying its GWP by a factor of12/44 (The Intergovernmental Panel on Climate Change (IPCC), ClimateChange 1995: The Science of Climate Change, 1996, p. 121). Methane(CH₄), a more potent GHG, is produced when organic waste decomposes inan oxygen free (anaerobic) environment, such as a landfill. Methane fromlandfills is the largest source of methane in the US.

The greater GHG emission reductions are usually obtained when recycledwaste materials are processed and used to replace fossil fuels. If thereplaced material is biogenic (material derived from living organisms),it is not always possible to obtain reductions of emissions. Even otherfactors, such as the treatment of the waste material and the fate of theproducts after the use, affect the emissions balance. For example, therecycling of oil-absorbing sheets made of recycled textiles lead toemission reductions compared with the use of virgin plastic. In anotherexample, the use of recycled plastic as raw material for constructionmaterial was found to be better than the use of impregnated wood. Thisis because the combustion of plastic causes more emissions thanimpregnated wood for reducing emissions. If the replaced material hadbeen fossil fuel-based, or concrete, or steel, the result would probablyhave been more favorable to the recycling of plastic.

Given the effect of GHGs on the environment, different levels ofgovernment are considering, and in some instances have initiated,programs aimed at reducing the GHGs released into the atmosphere duringthe conversion of fuels into energy. One such initiative is the RegionalGreenhouse Gas Initiative (RGGI). RGGI is a market-based programdesigned to reduce global warming pollution from electric power plantsin the Northeast. Other such initiatives are being considered indifferent sections of the U.S. and on the federal level. RGGI is agovernment mandated GHG trading system in the Northeastern U.S. Thisprogram will require, for example, that coal-fired power plantsaggressively reduce their GHG emissions by on average 2.5% per year. Oneway to do this is by changing the fuel source used or scrubbing theemissions to remove the pollutants. An alternative is to purchase carboncredits generated by others which can offset their emissions into theatmosphere.

Other emissions to be avoided are sulfur emissions as well as chlorineemissions. Fuels and waste containing significant amounts of sulfur orchlorine should be avoided for combustion and gasification reactions.Significant amounts are defined as an amount that when added to a finalfuel feed stock causes the final feed stock to have more than 2% sulfuror more than 1% of chlorine. Materials such as coal, used tires, carpet,and rubber, when combusted, release unacceptable amounts of harmfulsulfur- and chlorine-based gases.

Thus, there is a need for alternative fuels that burn efficiently andcleanly and that can be used for the production of energy and/orchemicals. There is at the same time a need for waste management systemsthat implement methods for reducing GHG emissions of waste by utilizingsuch wastes. In particular, there is a need for reducing the carbon footprint of materials by affecting their end-stage life cycle management.By harnessing and using the energy content contained in waste, it ispossible to reduce GHG emissions generated during the processing ofwastes and effectively use the waste generated by commercial andresidential consumers.

It is an object of the present invention to provide an engineered fuelfeed stock (EF) containing specified chemical molecular characteristics,such as carbon content, hydrogen content, oxygen content, sulfurcontent, ash content, moisture content, and HHV for thermal-conversionof carbon-containing materials. The engineered fuel feed stock is usefulfor many purposes including, but not limited to, production of synthesisgas. Synthesis gas, in turn, is useful for a variety of purposesincluding for production of liquid fuels by Fischer-Tropsch technology.

SUMMARY OF THE INVENTION

The present disclosure describes an engineered fuel feed stockcomprising at least one component derived from a processed MSW wastestream, the feed stock possessing a range of chemical molecularcharacteristics which make it useful for a variety of combustion andgasification purposes. Purposes such as generating energy when used as asubstitute for coal or as a supplement to coal is described, as well asa source feed stock for use in gasification and production of synthesisgas. The feed stock can be in the form of loose material, densifiedcubes, briquettes, pellets, or other suitable shapes and forms. Aprocess of producing engineered fuel feed stock is described whichcomprises the process in which a plurality of waste streams, includingsolid and liquid wastes, are processed and, where necessary, separatedin a materials recovery center so as to inventory the components whichcomprise the waste streams. In some embodiments, the materialscomprising the waste stream in the materials recovery facility areinventoried for chemical molecular characteristics, without separation,and this inventoried material can be stored for subsequent use whenproducing a desired engineered fuel feed stock having a particularchemical molecular profile. In other embodiments, the materialscomprising the waste stream entering the materials recovery facility areseparated according to their chemical molecular characteristics andinventoried separately for use in producing an engineered fuel feedstock. These materials comprising the waste stream entering thematerials recovery facility, when undergoing separation, can bepositively or negatively selected for, based on, for example, BTU fuelcontent, carbon content, hydrogen content, ash content, chlorinecontent, or any other suitable characteristics, for gasification orcombustion. Methods for making the engineered fuel feed stock describedherein are also described.

Algorithms for engineering HHV fuels are disclosed. HHV fuels can bedesigned, for example, to have the highest possible heat content with atolerable ash content in order to prevent slagging. These fuels havecomparable energy density (BTU/lb) to coal, but without the problems ofslagging, fusion and sulfur pollution, and can serve as a substitute forcoal or a supplement to coal. Also, engineered fuel feed stocks can bedesigned, for example, to produce high quality syngas by optimizing thecontent of C, H, and O in the feed stock prior to gasification. Suchengineered fuel feed stocks produce high quality syngas in terms of HHVif the syngas is to be used for power generation applications or H₂/COratios, amounts of CO and H₂ present in the product syngas in the eventthat the syngas is to be used in chemical synthetic applications. Also,engineered fuel feed stocks can be engineered so as to minimize harmfulemissions, for example, engineered feed stocks comprising less than 2%sulfur content. Various waste stream components, including recyclablematerials and recycling residue, can be used to produce the desiredengineered fuel feed stock. Although at any given time during the lifecycle of the waste entering the materials recovery facility, it may bedetermined that the highest and best use for some or all of thecomponents of the waste streams is for them to be recycled.

Accordingly, in one aspect the present invention provides an engineeredfuel feed stock, comprising a component derived from a processed MSWwaste stream, the feed stock having a carbon content of between about30% and about 80%, a hydrogen content of between about 3% and about 10%,an ash content of less than about 10%, a sulfur content of less than 2%,and a chlorine content of less than about 1%. In some embodiments, thefeed stock has a HHV of between about 3,000 BTU/lb and about 15,000BTU/lb. In some embodiments, the feed stock has a volatile mattercontent of about 40% to about 80%. In some embodiments, the feed stockhas a moisture content of less than about 30%. In some embodiments, thefeed stock has a moisture content of between about 10% and about 30%. Inother embodiments, the feed stock has a moisture content of betweenabout 10% and about 20%. In still further embodiments, the feed stockhas a moisture content of about 1% and about 10%. The engineered fuelfeed stock contains substantially no glass, metal, grit andnoncombustibles (other than those necessary to cause the engineered fuelfeed stock to be inert).

in some embodiments, the feed stock has a carbon content of betweenabout 40% and about 70%. In some embodiments, the feed stock has acarbon content of between about 50% and about 60%. In some embodiments,the feed stock has a carbon content of between about 30% and about 40%.In some embodiments, the feed stock has a carbon content of betweenabout 40% and about 50%. In some embodiments, the feed stock has acarbon content of between about 60% and about 70%. In some embodiments,the feed stock has a carbon content of between about 70% and about 80%.In some embodiments, the feed stock has a carbon content of about 35%.In some embodiments, the feed stock has a carbon content of about 45%.In some embodiments, the feed stock has a carbon content of about 55%.In some embodiments, the feed stock has a carbon content of about 65%.In some embodiments, the feed stock has a carbon content of about 75%.

In some embodiments, the feed stock has a hydrogen content of betweenabout 4% and about 9%. In some embodiments, the feed stock has ahydrogen content of between about 5% and about 8%. In some embodiments,the feed stock has a hydrogen content of between about 6% and about 7%.

In some embodiments, the feed stock has a moisture content of betweenabout 12% and about 28%. In some embodiments, the feed stock has amoisture content of between about 14% and about 24%. In someembodiments, the feed stock has a moisture content of between about 16%and about 22%. In some embodiments, the feed stock has a moisturecontent of between about 18% and about 20%.

In some embodiments, the feed stock has an ash content of less thanabout 10%. In some embodiments, the feed stock has an ash content ofless than about 9%. In some embodiments, the feed stock has an ashcontent of less than about 8%. In some embodiments, the feed stock hasan ash content of less than about 7%. In some embodiments, the feedstock has an ash content of less than about 6%. In some embodiments, thefeed stock has an ash content of less than about 5%. In someembodiments, the feed stock has an ash content of less than about 4%. Insome embodiments, the feed stock has an ash content of less than about3%.

In some embodiments, the feed stock has a HHV of between about 3,000BTU/lb and about 15,000 BTU/lb. In some embodiments, the feed stock hasa HHV of between about 4,000 BTU/lb and about 14,000 BTU/lb. In someembodiments, the feed stock has a HHV of between about 5,000 BTU/lb andabout 13,000 BTU/lb. In some embodiments, the feed stock has a HHV ofbetween about 6,000 BTU/lb and about 12,000 BTU/lb. In some embodiments,the feed stock has a HHV of between about 7,000 BTU/lb and about 11,000BTU/lb. In some embodiments, the feed stock has a HHV of between about8,000 BTU/lb and about 10,000 BTU/lb. In some embodiments, the feedstock has a HHV of about 9,000 BTU/lb.

In some embodiments, the feed stock has a volatile matter content ofabout 50% to about 70%. In some embodiments, the feed stock has avolatile matter content of about 60%.

in some embodiments, the engineered fuel feed stock has a ratio of H/Cfrom about 0.025 to about 0.20. In some embodiments, the engineered fuelfeed stock has a ratio of H/C from about 0.05 to about 0.18. In someembodiments, the engineered fuel feed stock has a ratio of H/C fromabout 0.07 to about 0.16. In some embodiments, the engineered fuel feedstock has a ratio of H/C from about 0.09 to about 0.14. In someembodiments, the engineered fuel feed stock has a ratio of H/C fromabout 0.10 to about 0.13. In some embodiments, the engineered fuel feedstock has a ratio of H/C from about 0.11 to about 0.12. In someembodiments, the engineered fuel feed stock has a ratio of H/C of about0.13. In some embodiments, the engineered fuel feed stock has a ratio ofH/C of about 0.08.

In some embodiments, the engineered fuel feed stock has an O/C ratiofrom about 0.01 to about 1.0. In some embodiments, the engineered fuelfeed stock has an O/C ratio from about 0.1 to about 0.8. In someembodiments, the engineered fuel feed stock has an O/C ratio from about0.2 to about 0.7. In some embodiments, the engineered fuel feed stockhas an O/C ratio from about 0.3 to about 0.6. In some embodiments, theengineered fuel feed stock has an O/C ratio from about 0.4 to about 0.5.In some embodiments, the engineered fuel feed stock has an O/C ratio ofabout 0.9. In some embodiments, the engineered fuel feed stock has anO/C ratio of about 0.01.

In some embodiments, the engineered fuel feed stock upon gasification at850° C. and an ER of 0.34 produces synthesis gas comprising H₂ in anamount from about 6 vol. % to about 30 vol. %; CO in an amount fromabout 14 vol. % to about 25 vol. %, CH₄ in an amount from about 0.3 vol.% to about 6.5 vol. %, CO₂ in an amount from about 6.5 vol. % to about13.5% vol. %; and N₂ in an amount from about 44 vol. % to about 68 vol.%.

In some embodiments, the engineered fuel feed stock upon gasification at850° C. and an ER of 0.34 produces synthesis gas having an H₂/CO ratiofrom about 0.3 to about 2.0. In some embodiments, the engineered fuelfeed stock upon gasification at 850° C. and an ER of 0.34 producessynthesis gas having an H₂/CO ratio from about 0.5 to about 1.5. In someembodiments, the engineered fuel feed stock upon gasification at 850° C.and an ER of 0.34 produces synthesis gas having an H₂/CO ratio fromabout 0.8 to about 1.2. In some embodiments, the engineered fuel feedstock upon gasification at 850° C. and an ER of 0.34 produces synthesisgas having an H₂/CO ratio of about 1.0.

In some embodiments, the engineered fuel feed stock upon gasification at850° C. and an ER of 0.34 produces synthesis gas having H₂ in an amountof about 20 vol. %; N₂ in an amount of about 46 vol. %; CO in an amountof about 25 vol. %; CH₄ in an amount of about 1 vol. %; CO₂ in an amountof about 8 vol. %; and a BTU/scf of about 160.

In some embodiments, the engineered fuel feed stock when combustedproduces less harmful emissions as compared to the combustion of coal.In some embodiments, the engineered fuel feed stock when combustedproduces less sulfur emission as compared to the combustion of coal. Insome embodiments, the engineered fuel feed stock when combusted producesless HCl emission as compared to the combustion of coal. In someembodiments, the engineered fuel feed stock when combusted produces lessheavy metal emissions such as for example mercury as compared to thecombustion of coal. In some embodiments, the engineered fuel feed stockis designed to avoid the emission of particulate matters, NOx, CO, CO₂,volatile organic compounds (VOCs), and halogen gases.

In some embodiments, the engineered fuel feed stock is designed to havereduced emission profiles with respect to GHGs as compared to the GHGsemitted from combusted coal. In some embodiments, the engineered fuelfeed stock is designed to have reduced emission profiles with respect toGHGs emitted from the combustion of biomasses such as for example, wood,switch grass and the like.

In some embodiments, the feed stock is in a loose, non-densified form.In other embodiments, the engineered fuel feed stock is in a densifiedform. In some embodiments, the densified form is a cube. In someembodiments, the densified form is rectangular. In other embodiments,the densified form is cylindrical. In some embodiments, the densifiedform is spherical. In some embodiments, the densified form is abriquette. In other embodiments, the densified form is a pellet. In someembodiments, the densified fuel is sliced into sheets of differentthickness. In some embodiments, the thickness is between about 3/16inches to about ¾ inches. In some embodiments, the engineered fuel feedstock further comprises at least one waste material in addition to thecomponent derived from a processed MSW waste stream that enhances thegasification of the fuel pellet. In some embodiments, the engineeredfuel feed stock further comprises at least one waste material inaddition to the component derived from a processed MSW waste stream thatenhances the gasification of the fuel pellet. In some embodiments, theenhancement is a reduction in ash. In other embodiments, the enhancementaids in the control of temperature. In still other embodiments, theenhancement is a reduction in the amount of sulfur emissions produced.In still other embodiments, the enhancement is the reduction of chlorineemissions produced. In still other embodiments, the enhancement is thereduction of heavy metal emissions produced.

In some embodiments, the engineered fuel feed stock is rendered inert.In some embodiments, the engineered fuel feed stock comprises at leastone additive that renders the feed stock inert. In some embodiments, anadditive can be blended into the processed MSW waste stream that canrender the resulting pellet inert. Some types of wet MSW contain arelatively high number of viable bacterial cells that can generate heatand hydrogen gas during fermentation under wet conditions, for exampleduring prolonged storage or transportation. For example, an additivesuch as calcium hydroxide can be added to the MSW for the prevention ofthe rotting of food wastes and for the acceleration of drying of solidwastes. In some embodiments, the additive that renders the feed stockinert is CaO. Other non limiting examples of additives are calciumsulfoaluminate and other sulfate compounds, as long as they do notinterfere with the downstream processes in which the pellet are used.

Alternatively, the MSW can be rendered biologically inert through anyknown method for inactivating biological material. For example, X-rayscan be used to deactivate the MSW before processing, or afterprocessing. Drying can be used to remove the water necessary fororganisms such as microbes to grow. Treatment of the MSW with high heatand optionally also high heat under pressure (autoclaving) will alsorender the MSW biologically inert. In one embodiment, the excess heatgenerated by the reciprocating engines or turbines fueled by theengineered pellets can be redirected through the system and used torender the MSW inert. In other embodiments, the feed stock is renderedinert through means such as microwave radiation.

In some embodiments, the densified form of the engineered fuel feedstock has a diameter of between about 0.25 inches to about 1.5 inches.In some embodiments, the densified form of the engineered fuel feedstock has a length of between about 0.5 inches to about 6 inches. Insome embodiments, the densified form of the engineered fuel feed stockhas a surface to volume ratio of between about 20:1 to about 3:1. Insome embodiments, the densified form of the engineered fuel feed stockhas a bulk density of about 10 lb/ft³ to about 75 lb/ft³. In someembodiments, the densified form of the engineered fuel feed stock has aporosity of between about 0.2 and about 0.6. In some embodiments, thedensified form of the engineered fuel feed stock has an aspect ratio ofbetween about 1 to about 10. In some embodiments, the densified form ofthe engineered fuel feed stock has a thermal conductivity of betweenabout 0.023 BTU/(ft·hr·° F.) and about 0.578 BTU/(ft·hr·° F.). In someembodiments, the densified form of the engineered fuel feed stock has aspecific heat capacity of between about 4.78×10⁻⁵ BTU/(lb·° F.) to4.78×10⁻⁴ BTU/(lb·° F.). In some embodiments, the densified form of theengineered fuel feed stock has a thermal diffusivity of between about1.08×10⁻⁵ ft²/s to 2.16×10⁻⁵ ft²/s.

In some embodiments, the at least one waste material that enhances thegasification of the fuel pellet is selected from fats, oils and grease(FOG). In some embodiments, the at least one waste material thatenhances the gasification of the fuel pellet is sludge. In someembodiments, the densified form of the engineered fuel feed stock issubstantially encapsulated within the FOG component. In some of theembodiments, the encapsulation layer is scored. In still furtherembodiments, the scoring of the encapsulated densified form of theengineered fuel feed stock causes the fuel to devolatize moreefficiently during gasification process than the fuel without thescoring.

In another aspect, an engineered fuel feed stock having a carbon contentof between about 30% and about 80%, a hydrogen content of between about3% and about 10%, a moisture content of between about 10% and about 30%,an ash content of less than about 10%, a sulfur content of less than 2%,and a chlorine content of less than about 1% is described that isproduced by a process comprising:

-   -   a) receiving a plurality of MSW waste feeds at a material        recovery facility;    -   b) inventorying the components of the plurality of MSW waste        feeds of step a) as they pass through a material recovery        facility based on the chemical molecular characteristics of the        components;    -   c) comparing the chemical molecular characteristics of the        components of the plurality of MSW waste feeds inventoried in        step b) with the chemical molecular characteristics of the        engineered fuel feed stock;    -   d) optionally adding additional engineered fuel feed stock        components which contain chemical molecular characteristics,        whose sum together with the inventoried components of step b)        equal the chemical molecular characteristics of the engineered        fuel feed stock. In some embodiments, the feed stock has a HHV        of between about 3,000 BTU/lb and about 15,000 BTU/lb. In some        embodiments, the feed stock has a volatile matter content of        about 40% to about 80%. In some embodiments, the engineered fuel        feed stock is reduced in size in order to homogenize the feed        stock. In some embodiments, the engineered fuel feed stock is        densified. In some embodiments, the densified feed stock is in        the form of a briquette. In some embodiments, the densified feed        stock is in the form of a pellet. In some embodiments, the        densified feed stock is in the form of a cube.

In another aspect, an engineered fuel feed stock is described that isproduced by a process comprising:

-   -   a) separating a plurality of MSW waste feeds at a material        recovery facility into a plurality of MSW waste components based        on chemical molecular characteristics;    -   b) selecting chemical molecular characteristics for the        engineered fuel feed stock comprising a carbon content of        between about 30% and about 80%, a hydrogen content of between        about 3% and about 10%, a moisture content of between about 10%        and about 30%, an ash content of less than about 10%, a sulfur        content of less than 2%, and a chlorine content of less than        about 1% for the engineered fuel feed stock;    -   c) selecting MSW waste components from step a) whose sum of        chemical molecular characteristics equals the chemical molecular        characteristics selected in step b);    -   d) optionally adding other fuel components to the selections of        step c) if the chemical molecular characteristics of the MSW        waste components selected in step c) do not equal the chemical        molecular characteristics of the selection of step b); and    -   e) mixing the components of step c) and optionally of step d).

In some embodiments, the size of the mixture of step e) is reduced tohelp homogenize the engineered fuel feed stock. In some embodiments, asize and shape is determined for a densified form of the mixture of stepe) or the size-reduced mixture of step e). In some embodiments, themixture of step c) is densified. In other embodiments, the size-reducedmixture of step e) is densified. In some embodiments, the engineeredfuel feed stock has a HHV of between about 3,000 BTU/lb and about 15,000BTU/lb. In some embodiments, the feed stock has a volatile mattercontent of about 40% to about 80%.

In another aspect, a method of producing an engineered fuel feed stockfrom a processed MSW waste stream is described which comprises the stepsof:

-   -   a) selecting a plurality components from a processed MSW waste        stream which components in combination have chemical molecular        characteristics comprising a carbon content of between about 30%        and about 80%, a hydrogen content of between about 3% and about        10%, a moisture content of between about 10% and about 30%, an        ash content of less than 10%, and a sulfur content of less than        2%;    -   b) combining and mixing together the selected components of        step a) to form a feed stock;    -   c) comparing the resulting chemical molecular characteristics of        the feed stock of step b) with the chemical molecular        characteristics of step a);    -   d) optionally adding other fuel components to the selected        components of step b) if the chemical molecular characteristics        of the MSW waste components selected in step b) do not equal the        chemical molecular characteristics of step a).

In some embodiments, the size of the mixture of step b) or step d) isreduced to help homogenize the engineered fuel feed stock. In someembodiments, a size and shape is determined for a densified form of themixture of step b) or the size-reduced mixtures of steps b) or d). Insome embodiments, the mixture of step b) is densified. In otherembodiments, the size-reduced mixture of step e) is densified to adensity of about 10 lbs/ft³ to about 75 lbs/ft³. In some embodiments,the engineered fuel feed stock has a HHV of between about 3,000 BTU/lband about 15,000 BTU/lb. In some embodiments, the feed stock has avolatile matter content of about 40% to about 80%.

In another aspect, a method of producing a engineered fuel feed stock isdescribed, the method comprising:

-   -   a) receiving a plurality of MSW waste streams;    -   b) selecting for the engineered fuel feed stock chemical        molecular characteristics comprising a carbon content of between        about 30% and about 80%, a hydrogen content of between about 3%        and about 10%, a moisture content of between about 10% and about        30%, an ash content of less than 10%, and a sulfur content of        less than 2%;    -   c) inventorying the components of the plurality of MSW waste        streams based on the chemical molecular characteristics of the        components;    -   d) comparing the chemical molecular characteristics of the        inventoried components of the plurality of MSW waste streams of        step c) with the selected chemical molecular characteristics of        step b); and    -   e) optionally adding additional fuel components with the        required chemical molecular characteristics to inventoried        components of step c) to meet the desired chemical molecular        characteristics of step b) for the engineered fuel feed stock.        In some embodiments, the engineered fuel feed stock of steps c)        or e) is mixed. In some embodiments, the engineered fuel feed        stock of steps c) or e) is reduced in size. In some embodiments,        the engineered fuel feed stock of steps c) or e) are densified.        In some embodiments, the size-reduced engineered fuel feed stock        of steps c) or e) are densified. In some embodiments, the        engineered fuel feed stock is densified to about 10 lbs/ft³ to        about 75 lbs/ft³.

In some embodiments, the engineered fuel feed stock is densified to forma briquette. In other embodiments, the engineered fuel feed stock isdensified to form of a pellet.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by the embodiments shown in thedrawings, in which:

FIG. 1 shows commonly available feed stock materials, such as, forexample, coal, FOGs, wood, sludge, black liquor, rubber and MSW streams,positioned in terms of their hydrogen content to carbon content ratio(H/C) (lb/lb) and oxygen content to carbon content (O/C) (lb/lb) ratio.

FIG. 2 shows some novel engineered fuel feed stocks produced byselecting known engineered fuel feed stocks within the dotted line anddirectly mixing the selected feed stocks, and in some cases increasingor decreasing the moisture content.

FIG. 3 shows a schematic with direct combustion of feed stock.

FIG. 4 shows a schematic with direct combustion of wet feed stock,without reducing its moisture content.

FIG. 5 shows the predicted effect of moisture on gasificationtemperature, carbon conversion and H₂+CO production rate for a typicalcoal feed stock at a constant air equivalence (ER) ratio (ER=0.34).

FIG. 6 shows the predicted variation of syngas compositions with feedstocks of different moisture contents for a typical wood feed stock at800° C.

FIG. 7 shows the predicted effect of fuel moisture content on carbonconversion, cold gas efficiency and CO+H₂ production rate for a typicalcoal feed stock at 850° C.

FIG. 8 shows the predicted effect of fuel moisture content on carbonconversion, cold gas efficiency and CO+H₂ production rate for purecarbon at 1000° C.

FIG. 9 shows the predicted total and external water supply required toproduce a syngas of H₂/CO=2.0 at 850° C. for a typical wood feed stock.

FIG. 10 shows the predicted CO+H₂ production rate, cold gas efficiencyand H₂/CO ratio at 850° C. and an ER=0.30 for a typical wood feed stock.

FIG. 11 provides a graphical representation of eq. 2 showing the weightfraction of various products as a function of the chain growth parameterα.

FIG. 12 provides predicted C/H and C/O ratios needed in feed stock forthe production of syngas with varying H₂/CO ratios.

FIG. 13 provides a graph showing cylindrical diameter plotted againstthe sphericity, the cylindrical length and specific area.

FIG. 14 provides a graph of feed stock containing different carbon andhydrogen contents and their predicted production of CO and H₂ during airgasification.

FIG. 15 provides a graph of feed stock containing different carbon andhydrogen contents and their predicted production of CO and H₂ duringair/steam gasification.

DETAILED DESCRIPTION OF TILE INVENTION

Novel engineered fuel feed stocks are provided that comprise at leastone waste stream component derived from MSW, such as recycling residuewhich is the non-recoverable portion of recyclable materials, and whichare engineered to have predetermined chemical molecular characteristics.These feed stocks can possess the chemical molecular characteristics ofbiomass fuels such as, for example, wood and switch grass, and, can alsohave the positive characteristics of high BTU containing fuels such as,for example, coal, without the negative attributes of coal such asdeleterious sulfur emissions. Also described are novel engineered fuelfeed stocks that comprise chemical molecular characteristics notobserved in natural fuels such as, for example, biomass, coal, orpetroleum fuels. These novel fuels contain, for example, unique ratiosof carbon, hydrogen, sulfur, and ash, such that, when compared to knownfuels, they provide a different combustion or gasification profile.Since these novel feed stocks have different combustion or gasificationprofiles, they provide novel fuels for many different types ofcombustors and gasifiers which, while functioning adequately due to theuniformity of the natural fuel, do not function optimally due to theless than optimized chemical molecular characteristics of natural fuels.Engineered fuel feed stocks such as those useful for the production ofthermal energy, power, biofuels, petroleum, and chemicals can beengineered and synthesized according to the methods disclosed herein.

Highly variable and heterogeneous streams of waste can now be processedin a controlled manner and a plurality of the resulting componentstherefrom recombined into an engineered fuel feed stock which behaves asa constant and homogeneous fuel for use in subsequent conversionprocesses. Included among these processes are pyrolysis, gasificationand combustion. The engineered fuel feed stock can be used alone toproduce thermal energy, power, biofuels, or chemicals, or it can be usedas a supplement along with other fuels for these and other purposes.Methods and processes for engineering homogeneous engineered fuel feedstock from naturally heterogeneous and variable waste streams whichpossess a variety of optimal physical and chemical characteristics fordifferent conversion processes are described, as well as different feedstocks themselves.

Chemical properties can be engineered into the resulting engineered fuelfeed stocks based on the type of conversion process for which the fuelwill be used. Feed stocks can be engineered for use as fuels includingsynthetic fuels, high BTU containing fuels fuels) and fuels useful toproduce high quality syngas, among other types of useful fuels. Forexample, engineered fuels can be designed to have the same or similarchemical molecular compositions as known solid fuels, such as, forexample, wood, coal, coke, etc. and function as a substitute for, orsupplemental to, fuel for combustion and gasification. Other fuels canbe designed and synthesized which have chemical molecularcharacteristics that are different than naturally occurring fuel. Forexample, High BTU Fuels can be designed to have the highest possibleheat content with a tolerable ash content in order to prevent slagging.These fuels have comparable energy density (such as carbon content,hydrogen content) as coal, but without the problems of slagging, fusionand sulfur pollution (ash content, sulfur content, and chlorine content)and can serve as a substitute for coal, or a supplement to coal. Fuelscan be designed to produce high quality syngas by optimizing, forexample, the content of C, H, O, moisture, and ash in the engineeredfuel feed stock. Such fuels produce high quality syngas in terms of, forexample, syngas caloric value, H₂/CO ratios, and amounts of CO, H₂, CO₂,and CH₄. These fuels that produce high quality syngas enable the stableoperation of gasifiers due to no, or minimal, slag formation and thelowest tar formation (at the appropriate gasifier temperatures). Thermalconversion devices are described in the art which are designed to suitspecific fuels found in the nature and in these cases operationalproblems often occur or modifications are needed to the devices whenfuels other than the designed for fuels are co-fired. The presentinvention provides for an optimal fuel to be engineered that will bestsuit known thermal conversion devices and no modifications to the devicewill be needed.

The engineered fuel feed stock described herein provides an efficientway to moderate the operating conditions of thermal conversion devicessuch as for example by lower the operating temperature, by reducing theneed for oxygen supply or steam supply, by allowing for the relaxing ofemission controls. The methods described herein provide a powerful meansfor upgrading low-grade fuels such as sludge, yardwastes, food wastesand the like to be transformed into a high quality fuel.

The following specification describes the invention in greater detail.

DEFINITIONS

The term “air equivalence ratio” (ER) means the ratio of the amount ofair supplied to the gasifier divided by the amount of air required forcomplete fuel combustion. Air equivalence ratio, “ER,” can berepresented by the following equation:

${E\; R} = \frac{{Air}\mspace{14mu} {supplied}\mspace{14mu} {to}\mspace{14mu} {the}\mspace{14mu} {gasifier}}{{Air}\mspace{14mu} {required}\mspace{14mu} {for}\mspace{14mu} {complete}\mspace{14mu} {fuel}\mspace{14mu} {combustion}}$

The term “British Thermal Unit” (BTU) means the amount of heat energyneeded to raise the temperature of one pound of water by one degree F.

The term “carbon boundary” means the temperature obtained when exactlyenough oxygen is added to achieve complete gasification, or carbonconversion. Above this temperature there is no solid carbon present.

The term “carbon content” means all carbon contained in the fixed carbon(see definition below) as well as in all the volatile matters in thefeed stock.

The term “carbon conversion” means to convert solid carbon in fuel feedstock into carbon-containing gases, such as CO, CO2 and CH4 in mostgasification operations

The term “commercial waste” means solid waste generated by stores,offices, restaurants, warehouses, and other non-manufacturing,non-processing activities. Commercial waste does not include household,process, industrial or special wastes.

The term “construction and demolition debris” (C&D) means uncontaminatedsolid waste resulting from the construction, remodeling, repair anddemolition of utilities, structures and roads; and uncontaminated solidwaste resulting from land clearing. Such waste includes, but is notlimited to bricks, concrete and other masonry materials, soil, rock,wood (including painted, treated and coated wood and wood products),land clearing debris, wall coverings, plaster, drywall, plumbingfixtures, nonasbestos insulation, roofing shingles and other roofcoverings, asphaltic pavement, glass, plastics that are not sealed in amanner that conceals other wastes, empty buckets ten gallons or less insize and having no more than one inch of residue remaining on thebottom, electrical wiring and components containing no hazardousliquids, and pipe and metals that are incidental to any of the above.Solid waste that is not C&D debris (even if resulting from theconstruction, remodeling, repair and demolition of utilities, structuresand roads and land clearing) includes, but is not limited to asbestoswaste, garbage, corrugated container board, electrical fixturescontaining hazardous liquids such as fluorescent light ballasts ortransformers, fluorescent lights, carpeting, furniture, appliances,tires, drums, containers greater than ten gallons in size, anycontainers having more than one inch of residue remaining on the bottomand fuel tanks. Specifically excluded from the definition ofconstruction and demolition debris is solid waste (including whatotherwise would be construction and demolition debris) resulting fromany processing technique, that renders individual waste componentsunrecognizable, such as pulverizing or shredding.

The term “devolatization” means a process that removes the volatilematerial in a engineered fuel feed stock thus increasing the relativeamount of carbon in the engineered fuel feed stock.

The term “fixed carbon” is the balance of material after moisture, ash,volatile mater determined by proximate analysis.

The term “garbage” means putrescible solid waste including animal andvegetable waste resulting from the handling, storage, sale, preparation,cooking or serving of foods. Garbage originates primarily in homekitchens, stores, markets, restaurants and other places where food isstored, prepared or served.

The term “gasification” means a technology that uses a noncombustionthermal process to convert solid waste to a clean burning fuel for thepurpose of generating for example, electricity, liquid fuels, and dieseldistillates. Noncombustion means the use of no air or oxygen orsubstoichiometric amounts of oxygen in the thermal process.

The term “hazardous waste” means solid waste that exhibits one of thefour characteristics of a hazardous waste (reactivity, corrosivity,ignitability, and/or toxicity) or is specifically designated as such bythe Environmental Protection Agency (EPA) as specified in 40 CFR part262.

The term “Heating Value” is defined as the amount of energy releasedwhen a fuel is burned completely in a steady-flow process and theproducts are returned to the state of the reactants. The heating valueis dependent on the phase of water in the combustion products. If H₂O isin liquid form, heating value is called HHV (Higher Heating Value). WhenH₂O is in vapor form, heating value is called LHV (Lower Heating Value).

The term “higher heating value” (HHV) means the caloric value releasedwith complete fuel combustion with product water in liquid state. On amoisture free basis, the HHV of any fuel can be calculated using thefollowing equation:

HHV_(Fuel)=146.58C+568.78H+29.4S−6.58A−51.53(O+N).

wherein C, H, S, A, O and N are carbon content, hydrogen content, sulfurcontent, ash content, oxygen content and nitrogen content, respectively,all in weight percentage.

The term “municipal solid waste” (MSW) means solid waste generated atresidences, commercial or industrial establishments, and institutions,and includes all processable wastes along with all components ofconstruction and demolition debris that are processable, but excludinghazardous waste, automobile scrap and other motor vehicle waste,infectious waste, asbestos waste, contaminated soil and other absorbentmedia and ash other than ash from household stoves. Used tires areexcluded from the definition of MSW. Components of municipal solid wasteinclude without limitation plastics, fibers, paper, yard waste, rubber,leather, wood, and also recycling residue, a residual componentcontaining the non-recoverable portion of recyclable materials remainingafter municipal solid waste has been processed with a plurality ofcomponents being sorted from the municipal solid waste.

The term “nonprocessable waste” (also known as noncombustible waste)means waste that does not readily gasify in gasification systems anddoes not give off any meaningful contribution of carbon or hydrogen intothe synthesis gas generated during gasification. Nonprocessable wastesinclude but are not limited to: batteries, such as dry cell batteries,mercury batteries and vehicle batteries; refrigerators; stoves;freezers; washers; dryers; bedsprings; vehicle frame parts; crankcases;transmissions; engines; lawn mowers; snow blowers; bicycles; filecabinets; air conditioners; hot water heaters; water storage tanks;water softeners; furnaces; oil storage tanks; metal furniture; propanetanks; and yard waste.

The term “processed MSW waste stream” means that MSW has been processedat, for example, a materials recovery facility, by having been sortedaccording to types of MSW components. Types of MSW components include,but are not limited to, plastics, fibers, paper, yard waste, rubber,leather, wood, and also recycling residue, a residual componentcontaining the non-recoverable portion of recyclable materials remainingafter municipal solid waste has been processed with a plurality ofcomponents being sorted from the municipal solid waste. Processed MSWcontains substantially no glass, metals, grit, or non-combustibles. Gritincludes dirt, dust, granular wastes such as coffee grounds and sand,and as such the processed MSW contains substantially no coffee grounds.

The term “processable waste” means wastes that readily gasify ingasification systems and give off meaningful contribution of carbon orhydrogen into the synthesis gas generated during gasification.Processable waste includes, but is not limited to, newspaper, junk mail,corrugated cardboard, office paper, magazines, books, paperboard, otherpaper, rubber, textiles, and leather from residential, commercial, andinstitutional sources only, wood, food wastes, and other combustibleportions of the MSW stream.

The term “pyrolysis” means a process using applied heat in anoxygen-deficient or oxygen-free environment for chemical decompositionof solid waste.

The term “recycling residue” means the residue remaining after arecycling facility has processed its recyclables from incoming wastewhich no longer contains economic value from a recycling point of view.

The term “sludge” means any solid, semisolid, or liquid generated from amunicipal, commercial, or industrial wastewater treatment plant orprocess, water supply treatment plant, air pollution control facility orany other such waste having similar characteristics and effects.

The term “solid waste” means unwanted or discarded solid material withinsufficient liquid content to be free flowing, including but notlimited to rubbish, garbage, scrap materials, junk, refuse, inert fillmaterial, and landscape refuse, but does not include hazardous waste,biomedical waste, septic tank sludge, or agricultural wastes, but doesnot include animal manure and absorbent bedding used for soil enrichmentor solid or dissolved materials in industrial discharges. The fact thata solid waste, or constituent of the waste, may have value, bebeneficially used, have other use, or be sold or exchanged, does notexclude it from this definition.

The term “steam/carbon ratio” (S/C) means the ratio of total moles ofsteam injected into the gasifier/combustor divided by the total moles ofcarbon feed stock. The steam/carbon ratio, “S/C,” can be represented bythe following equation:

${S\text{/}C} = \frac{{Total}\mspace{14mu} {moles}\mspace{14mu} {of}\mspace{14mu} {steam}}{{Total}\mspace{14mu} {moles}\mspace{14mu} {of}\mspace{14mu} {carbon}\mspace{14mu} {in}\mspace{14mu} {feed}\mspace{14mu} {stock}}$

The term “thermal efficiency” (also known as cold gas efficiency) meansthe ratio of the total HHV contained in the resulting product gasdivided by the total HHV that was contained in the fuel input. Thermalefficacy, “Eff,” can be represented by the following equation:

${Eff} = {\frac{{Total}\mspace{14mu} {HHV}\mspace{14mu} {of}\mspace{14mu} {synthesis}\mspace{14mu} {gas}}{{Total}\mspace{14mu} {HHV}\mspace{14mu} {of}\mspace{14mu} {fuel}\mspace{14mu} {input}} \times 100\%}$

The term “volatile materials” (also known as volatile organic compounds)means the organic chemical compounds that have high enough vaporpressures under normal conditions to significantly vaporize and enterthe atmosphere. Non-limiting examples of volatile materials includealdehydes, ketones, methane, and other light hydrocarbons.

Described herein are novel engineered fuel feed stocks comprising MSW,the feed stocks having any of a number of desired chemical molecularcharacteristics, including but not limited to carbon content, hydrogencontent, oxygen content, nitrogen content, ash content, sulfur content,moisture content, chlorine content, and HHV content. This feed stock isuseful for a variety of chemical conversion processes. Also describedare processes for producing an engineered fuel feed stock and methods ofmaking same.

One abundant source of engineered fuel feed stock is MSW. MSW is solidwaste generated at residences, commercial or industrial establishments,and institutions, and includes all processable wastes along with allcomponents of construction and demolition debris that are processable,but excluding hazardous waste, automobile scrap and other motor vehiclewaste, infectious waste, asbestos waste, contaminated soil and otherabsorbent media and ash other than ash from household stoves. It doesinclude garbage, refuse, and other discarded materials that result fromresidential, commercial, industrial, and community activities. Thecomposition of MSW varies widely depending on time of collection, seasonof the year of collection, the types of customers from which the MSW iscollected on any given day, etc. MSW may contain a very wide variety ofwaste or discarded material. For instance, the waste may includebiodegradable waste, non-biodegradable waste, ferrous materials,non-ferrous metals, paper or cardboard in a wide variety of forms, awide range of plastics (some of which may contain traces of toxic metalsused as catalysts, stabilizers or other additives), paints, varnishesand solvents, fabrics, wood products, glass, chemicals includingmedicines, pesticides and the like, solid waste of various types and awide range of other materials. The waste includes household waste andindustrial waste. Industrial waste contemplated for use herein is low intoxic or hazardous materials. However, MSW is processed in order toremove non-processable components prior to engineering the engineeredfuel feed stocks described herein.

Processed MSW has been sorted or inventoried according to types of MSWcomponents. Types of MSW components include, but are not limited to,plastics, fibers, paper, yard waste, rubber, leather, wood, and alsorecycling residue, a residual component containing the non-recoverableportion of recyclable materials remaining after municipal solid wastehas been processed with a plurality of components being sorted from themunicipal solid waste. Processed MSW contains substantially no glass,metals, grit, or non-combustibles. Grit includes dirt, dust, granularwastes such as coffee grounds and sand, and as such the processed MSWcontains substantially no coffee grounds. The term “substantially no” asused herein means that no more than 0.01% of the material is present inthe MSW components.

Another fuel source for use in an engineered fuel feed stock is FOGs.FOGs are commonly found in such things as meats, sauces, gravy,dressings, deep-fried foods, baked goods, cheeses, butter and the like.Many different businesses generate FOG wastes by processing or servingfood, including; eating and drinking establishments, caterers,hospitals, nursing homes, day care centers, schools and grocery stores.FOGs have been a major problem for municipalities. Studies haveconcluded that FOGs are one of the primary causes of sanitary sewerblockages which result in sanitary sewer system overflows (SSOs) fromsewer collection systems. These SSOs have caused numerous problems insome municipalities including overflow out of the sewage lines out ofmaintenance (manhole) holes and into storm drains. The water in stormdrains flows into the water ways and eventually into the ocean. SSOspose a threat to public health, adversely affect aquatic life, and areexpensive to clean up. The most prevalent cause of the SSOs is FOGaccumulation in the small to medium sewer lines serving food serviceestablishments. Thus a use as fuel would provide a means of disposal ofFOGs without the prevalence of SSOs occurring due to the discharge ofFOGs into the waste water.

Present methods of discarding FOGs, besides directly into the sewersystems, include landfills. While these types of wastes are generallyconsidered nuisances, they contain a high carbon content that can betransformed into a source of fuel.

Other types of oils and greases useful in the present invention arepetroleum waste products. Nonlimiting examples of petroleum wasteproducts include discarded engine oil.

Yet another type of waste useful in the production of engineered fuelfeed stock is biomass waste, also known as biogenic waste. Biomassrefers to living and recently dead biological material that can be usedas fuel or for industrial production. Most commonly, biomass refers toplant matter grown for use as biofuel, but it also includes plant oranimal matter used for production of fibers, chemicals or heat. Biomassmay also include biodegradable wastes that can be burnt as fuel. Itexcludes organic material which has been transformed by geologicalprocesses into substances such as coal or petroleum. Nonlimiting typesof biomass waste include woods, yard wastes, plants, includingmiscanthus, switchgrass, hemp, corn, poplar, willow, sugarcane and oilpalm (palm oil), coconut shells, and shells of nuts.

Yet another type of waste useful in the production of engineered fuelfeed stock is sludge. Sludge is a mixture of solid wastes and bacteriaremoved from the wastewater at various stages of the treatment process.It can be categorized as “primary sludge” and “secondary sludge”.Primary sludge is about 4% solids and 96% water. It consists of thematerial which settles out of wastewater in the primary sedimentationtanks, before bacterial digestion takes place. Secondary or activatedsludge is much more liquid—about 1% solids and 99% water. Secondarysludge consists of bacteria and organic materials on which the bacteriafeed. About 30% of the secondary sludge produced is returned to theaeration tanks to assist with the biological process of sewagetreatment. The remaining 70% must be disposed of.

The sludge contemplated for use in the present invention is municipalsludge a.k.a. biosolids. Municipal sludge does not include papermill orother industrial/agricultural sludge. The key determinants of thecaloric or BTU value of a sludge are its dryness expressed as TotalSolids on a wet weight basis (or inversely as water content) and itsvolatile solids content (Total Volatile Solids or TVS expressed on a dryweight basis). There are two distinct types of sludge—1) raw sludge(sludge treated only with primary and secondary aerobic clarifiers) and2) digested sludge (add anaerobic digestion to number 1). Anaerobicsludge is typically 60% TVS and raw sludge is typically 75-80% TVS. TheTS of sludge cake (dewatered sludge) varies depending on the method usedby the treatment plant to dewater the sludge, and ranges from 10% to97+%. One pound of Volatile Solids has about 10,000-12,000 BTU, e.g., itrequires 1,200 BTU to drive off 1 lb of water as steam.

Other types of materials useful in the production of engineered feedstocks described herein are animal wastes such as manures, animalbiomass (meat and bone tissue), poultry litter, fossil fuels such ascoal, coal by products, petroleum coke, black liquor, and carbon black.

Chemical compositions of fuel are known to affect reactor performance,whether for combustion or gasification, and therefore the production of,and quality of, syngas. Most gasifiers are constructed so as to be ableto efficiently burn one type of fuel—a homogeneous fuel, such as woodpellets or coal, for example. Although the natural fuels such as wood orcoal are homogeneous and provide the reactor with a constant supply ofpredictable fuel, these fuels do not allow the reactors to functionoptimally due to their suboptimal chemical molecular characteristics.

Furthermore, syngas, which results from the gasification process, can beused to produce, for example, diesel distillates and liquid fuels.Syngas useful in the production of such products should contain at leasta certain amount energy expressed usually in BTU/ft³ in order to be usedefficiently in liquid fuel production, while other syngas requirementsfor this process may also include an appropriate ratio of hydrogen tocarbon monoxide (H₂/CO), as well as syngas purity.

Engineered fuel feed stock is described herein which comprises at leastone component derived from a processed MSW waste stream and embodiespredetermined chemical molecular characteristics that cause the fuel toperform optimally for a particular thermal conversion process. Byselecting waste components from MSW so as to remove contaminating wastesthat do not contribute to the gasification process or create hazardousemissions (such as dioxins, mercury, sulfur and chlorine, etc.), andoptionally adding other materials that enhance the gasification orcombustion process, material useful for production of engineered fuelfeed stock with the appropriate chemical molecular characteristics isachieved.

FIG. 1 shows commonly available feed stock materials, such as, forexample, coal, FOGs, wood, sludge, black liquor, rubber and MSW streams,positioned in terms of their hydrogen content to carbon content ratio(H/C) (lb/lb) and oxygen content to carbon content (O/C) (lb/lb) ratio.When these natural feed stocks are surrounded on the graph by a solidline, an envelope is formed, which indicates the range of H/C and O/Cfor naturally occurring materials. FIG. 1 also plotted the carbonboundary temperature against the O/C ratio, with variations with H/Cindicated by a slashed area. The carbon boundary temperature is thetemperature obtained when exactly enough oxygen is added to achievecomplete carbon conversion. For biomass gasification the typicaltemperature is about 850° C. and for dry coal gasification the typicaltemperature is about 1,500° C. Fuels such as anthracite, semianthracite,high- and low-volatile bituminous all have low H/C ratios from about0.03 to 0.07 and low O/C content ratios from about 0.05 to about 0.12.These fuels require high temperatures due to the low O/C ratio andnormally require steam injection to promote complete conversion of thecarbon during gasification. Other feed stocks such as various woods,magazines, mixed paper, and corrugated cardboard all have relativelyhigh H/C content ratios of about 0.1 to about 0.14 and O/C contentratios of about 0.8 to about 1.0, which in practice require lowgasification temperatures. For feed stocks to be fully gasified at about850° C., it is seen from FIG. 1 that the O/C ratio in feed stock shouldbe about 0.55 to 0.6. For woody biomass feed stocks which have a O/Cratio of about 0.75 to 0.90, over-oxidizing (or increased oxidation) mayoccur at this temperature, and thus a higher CO₂ in the syngas would beexpected. Therefore, it is an advantage of the engineered feed stockthat fuel O/C and H/C ratios can be adjusted to allow for optimalgasification operation and performance to be achieved.

In FIG. 1, it can also be observed that H₂/CO production will varyaccording to H/C content, but only slightly with increasing O/C content.Also, FIG. 1 shows that Heating Value and H₂+CO production rate bothincrease with increasing H/C ratios and with decreasing O/C ratios.

By judiciously selecting engineered fuel feed stocks based on, forexample, their H/C ratio, O/C ratio, ash content and moisture content,the present inventors have discovered novel engineered fuel feed stocksthat can both simulate naturally occurring fuels, such as for examplewood and coal, as well as populate the carbon boundary with heretoforeunknown novel engineered fuel feed stocks that have differentgasification profiles as compared to known engineered fuel feed stocks.FIG. 2 shows some novel engineered fuel feed stocks produced byselecting known engineered fuel feed stocks within the dotted line anddirectly mixing the selected feed stocks, and in some cases increasingor decreasing the moisture content. These novel feed stocks populateareas within the solid lined area within the carbon temperatureboundary. Engineered fuel feed stock can be designed by selecting typesof feed stock characteristics identified within the carbon boundary ofthe graph based on, for example, H₂/CO content in the product syngas,H₂+CO production rate and Heating Value of the syngas, which wouldindicate the H/C ratio and O/C ratio required for a particularengineered fuel that should be best suited for a particular application.For various applications, such as, for example, gasification for energyproduction, gasification for Fischer-Tropsch fuel production, pyrolysis,and combustion different HHV contents, CO+H2 production rates or H₂/COratios may be required.

Chemical Properties of Fuel that Affect Gasification and Combustion ofthe Fuel

The combustion and gasification processes use fuel containing sufficientenergy that upon firing the fuel releases the stored chemical energy.This energy stored in the fuel can be expressed in terms of percentcarbon, hydrogen, oxygen, along with the effects of other componentssuch as sulfur, chlorine, nitrogen, and of course moisture in the formof H₂O.

As a possible fuel source, MSW can be characterized by its chemicalmolecular make up, such as, for example, the amount of carbon, hydrogen,oxygen, and ash present. However, MSW normally consists of a variety ofcomponents that can individually or collectively be characterizedthemselves for fuel purposes by a variety of parameters including,without limitation, carbon content, hydrogen content, moisture content,ash content, sulfur content, chlorine content, and HHV content. Althoughheterogeneic in nature, the many components of MSW can serve as rawmaterials for engineering various engineered fuel feed stocks useful fora variety of different thermal conversion processes. Such materials canbe engineered to create engineered fuel feed stocks that embody thechemical characteristics of known fuels, for example, wood and coal,while other feed stocks can be engineered to create fuels that are notobserved in nature and provide unique combustion and gasificationprofiles. For example, the carbon and hydrogen content of most biomassessuch as wood is given in Table 1. From Table 1 it can be readilyobserved that the range of carbon in biomass such as wood varies onlyslightly, as does the hydrogen content.

TABLE 1 C H O N S Ash Volatiles Name % % % % % % % HHV BTU/lb WOOD Beech51.64 6.26 41.45 0.00 0.00 0.65 — 8,762 Black Locust 50.73 5.71 41.930.57 0.01 0.80 80.94 8,474 Douglas Fir 52.30 6.30 40.50 0.10 0.00 0.8081.50 9,050 Hickory 47.67 6.49 43.11 0.00 0.00 0.73 — 8,672 Maple 50.646.02 41.74 0.25 0.00 1.35 — 8,581 Ponderosa Pine 49.25 5.99 44.36 0.060.03 0.29 82.54 8,607 Poplar 51.64 6.26 41.45 0.00 0.00 0.65 — 8,921 RedAlder 49.55 6.06 43.78 0.13 0.07 0.40 87.10 8,298 Redwood 53.50 5.9040.30 0.10 0.00 0.40 83.50 9,041 Western Hemlock 50.40 5.80 41.10 0.100.10 2.20 84.80 8,620 Yellow Pine 52.60 7.00 40.10 0.00 0.00 1.31 —9,587 White Fir 49.00 5.98 44.75 0.05 0.01 0.25 83.17 8,577 White Oak49.48 5.38 43.13 0.35 0.01 1.52 81.28 8,349 Madrone 48.94 6.03 44.750.05 0.02 0.20 87.80 8,388

Likewise the carbon content of most coals does not vary widely as seenin Table 2, and most examples of coal have similar if not identicalcarbon and hydrogen content,

TABLE 2 Heat content Name C H O S Volatiles BTU/lb Lignite¹   60-75  6.0-5.8  34-17  0.5-3 45-65 <12,240 Flame coal   75-82   6.0-5.8 >9.8 ~140-45 <14,130 Gas flame coal   85-87.5 5.6-5.0 7.3-4.5 ~1 28-35 <15,030Fat coal 87.5-89.5 5.0-4.5 4.5-3.2 ~1 19-28 <15,210 Forge coal 89.5-90.54.5-4.0 3.2-2.8 ~1 14-19 <15,210 Non baking coal 90.5-91.5 4.0-3.72.8-3.5 ~1 10-14 <15,210 Anthracite >91.5 <3.75 <2.5 ~1  7-12 <15,210¹Lindner E., Chemie für Ingenieure, Lindner Verlag Karlsruhe, (2007) p.258.

When used as a fuel source, for example, in gasification, the carbon andhydrogen content have a significant effect on the chemicalcharacteristics of the syngas. Thus, because the carbon and hydrogencontent of, for example, wood does not vary greatly, the process ofgasification must be varied so that the chemical characteristics of thesyngas can be varied. In contrast, the present invention allowsengineered fuel feed stocks to be engineered that not only contain thecarbon content of wood or coal, but also amounts of carbon and hydrogennot contained in biomasses such as wood or in fuels such as coal,thereby providing new fuels for gasification and combustion reactions.Thus, the present invention provides for engineered fuel feed stocks tobe engineered to contain a variety of carbon and hydrogen amounts beyondwhat is contained in naturally occurring fuels.

Effect of Feed Stock Moisture on Gasification and Combustion CombustionApplications

It is generally true that as moisture content increases in feed stock,the efficiency of the combustor or burner is reduced since some part ofthe heat released from feed stock will be consumed by evaporating thewater. However, in order to understand the impact of feed stock moistureon the efficiency of the combustion, an overall systems perspective mustbe developed.

The prior art has understood that moisture should, if not, must bereduced to low levels, such as below 10%, in order to have fuels thatwill allow for efficient firing of combustion reactors (see for exampleU.S. Pat. No. 7,252,691). However, consider a process (FIG. 3) in whichthe wet fuel is first dried using an energy stream Q₁, which isgenerally equal to the heat needed for vaporization of the water in thefuel and a sensible heat change resulting from the difference betweenthe feed stock inlet and outlet temperatures, in addition to heat lossesfrom the dryer. After drying, the water vapor is vented and the feedstock with reduced moisture content is sent to the combustor or boiler,where a heating load Q₂ is applied. The total net available energy isthen Q_(net)=Q₂−Q₁, which represents the effect of the additional energyneeded from the entire system for reducing the moisture content of thefuel.

By comparison, FIG. 4 shows a schematic with direct combustion of wetfeed stock, without reducing its moisture content. The available heatutilization is Q₃. In order to understand the impact of moisture on theengineered fuel feed stock a simulation using HYSYS (AspenTech, Inc.,Burlington Mass.) was performed under the following parameters. Feedstock with a moisture content of either 30 wt % or 40 wt %, was dried ata rate of one tone per hour to a moisture content of 10 wt %, i.e. 445lbs/hr or 667 lbs/hr of water removed (vaporized by heating to about250° F. This requires an input of energy of approximately 0.64 mmBTU/hror 0.873 mmBTU/hr, respectively. The feed stock at a moisture content of10 wt % is then combusted in a boiler assuming the heating load isadjusted to control the flue gas temperature to a predeterminedtemperature. Depending on the boiler or heat exchanger design, thispredetermined temperature could be higher (non-condensation, 150° F.) orlower (condensation, 100° F.) than the temperature of water in flue gas.The results are tabulated below in Table 3 and Table 4:

TABLE 3 Process Process with feed stock w/o feed stock drying dryingInitial feed stock moisture 30 30 (wt %) Final feed stock moisture 10 30Water vapor removed (lb/h) 445 0 Heat required for drying 0.640 0(mmBTU/h) Heat utilization from boiler 9.571 8.972 (mmBTU/h)(non-condensation) (non-condensation) 9.949 9.825 (condensation)(condensation) Net heat utilization 8.931 8.972 (mmBTU/h)(non-condensation) (non-condensation) 9.309 9.825 (condensation)(non-condensation) Heat utilization 71.3 71.6 efficiency (%)(non-condensation) (non-condensation) 74.3 78.4 (condensation)(condensation) Flue gas mass flow rate (lb/h) 12,642 13,087 Adiabaticflame temperature 2,725 2,445 (° F.) Thermal equilibrium CO 71 11production (ppm) Thermal equilibrium NO_(x) 2,311 1,212 production (ppm)Vapor content in flue gas (%) 8.9 13.8 CO₂ in flue gas (%) 13.7 13.0Assumptions: (1): the feed stock is assumed to have properties similarto wood (2): the combustion air is adjusted to have 8% O₂ in flue gas.

TABLE 4 Process Process with feed stock w/o feed stock drying dryingInitial feed stock moisture 40 40 (wt %) Final feed stock moisture 10 40Water vapor removed (lb/h) 667 0 Heat required for drying 0.873 0(mmBTU/h) Heat utilization from boiler 8.203 7.385 (mmBTU/h)(non-condensation) (non-condensation) 8.527 8.420 (condensation)(condensation) Net heat utilization 7.330 7.385 (mmBTU/h)(non-condensation) (non-condensation) 7.654 8.420 (condensation)(condensation) Heat utilization efficiency (%) 66.5 67.0(non-condensation) (non-condensation) 69.5 76.4 (condensation)(condensation) Flue gas mass flow rate (lb/h) 10,842 11,509 Adiabaticflame 2,723 2,273 temperature (° F.) Thermal equilibrium CO 71 2.9production (ppm) Thermal equilibrium NOx 2,306 764 production (ppm)Vapor content in flue gas (%) 8.9 17.3 CO2 in flue gas (%) 13.7 12.5Assumptions: (1): the feed stock is assumed to have properties similarto wood (2): the combustion air is adjusted to have 8% O₂ in flue gas.

The data in Tables 3 and 4 show the following.

(1) Without feed stock drying, the process generally provides betteroverall heat utilization. When heat losses from dryer and combustor areconsidered, the process without feed stock drying will be even better,because a larger heat loss would be expected when employing the dryerand combustor, since separate units will be in use, that together willhave a larger heat loss due to the increased surface area as compared tojust the combustor.

(2) With a higher water vapor presence in flue gas, the convective heattransfer can be improved due to increased mass flow rate of theconvective gas (flue gas), which improves the heat utilization.

(3) With a higher water vapor and lower CO₂ concentration, the radiationheat transfer between flue gas and heat transfer surface may also beincreased due to increased emissivity.

(4) Due to high water content in feed stock in case of without drying,the flame temperature is low compared to the case w/drying. As a result,the CO and NOx productions may be greatly reduced if the wet feed stockis directly combusted.

(5) When a feed stock dryer is utilized, the overall capital andoperating costs are increased.

Thus, the effect of moisture on combustion processes must be evaluatedin the overall system approach. Drying a feed stock prior to combustiondoes not necessarily result in savings or improvements in overall usableenergy, or increasing the overall energy utilization efficiency. Inaddition, adding the extra step of reducing the moisture content of fuelalso adds extra capital costs and operation and management costs.Burning a dry feed stock increases the potentials of air pollutantproductions including CO and NOx. This is consistent with the commoncounter measure seen in the industry whereby water is sprayed into theburner to lower the flame temperature so as to reduce slagging(formation of ash) and the negative effects of, among other things, theproduction of CO and NOx.

Conversely, if the moisture content in the fuel is too high (e.g.greater than about 50 wt %), the difficulty in maintaining stablecombustion significantly increases. Therefore, a moisture content ofabout 10 wt % to about 40 wt % has been found to be optimal forbalancing efficiency and reactor operation.

Gasification Applications

Moisture can effect gasification in a variety of ways. For example, ifmoisture is removed from the feed stock prior to being gasified,gasification performance may, or may not, be improved, depending uponwhich parameter of gasification is observed. In terms of energyutilization efficiency, drying may not improve the overall efficiency ofgasification, unlike the effect of drying the feed stock upon combustionapplications as discussed above.

Depending upon the gasification application, oxidants such as air, pureoxygen or steam can be used. In the case of oxygen large scale coalgasification which operates at temperatures of typically 1500° C., theoxygen consumption is high, which makes slagging and melting of ash anoperational challenge. The challenge in this case is operating thegasification with a minimum amount of gasifying feed stock requiredbecause this reduces the amount of oxygen per unit product gas. Thisreduction is oxygen translates into a larger savings during thegasification. However, with the reduction in oxygen as the oxidant, moresteam is then necessary. Since more moisture is necessary, it can eitherbe introduced into the gasification unit or as in the present inventionthe necessary moisture is present in the feed stock. This increase inmoisture in the feed stock, both reduces the amount of oxygen neededduring gasification as well as allows more control of the gasificationtemperature, which increases carbon conversion, and thus improves theoverall gasification performance.

Furthermore, the thermodynamics and kinetics of the gasificationreaction are effected by the amount of moisture during the gasificationreaction. Two reactions that occur during the gasification reaction aregiven below:

C+½O2=CO  (a)

C+H₂O=CO+H₂  (b)

Though the thermodynamics and kinetics dictate that most of thegasification will be accomplished via reaction (a), the reaction givenin (b) allows every carbon that is gasified via steam yields twomolecules of synthesis gas per atom of carbon with steam, which is lessextensive in comparison with only one carbon in reaction (a) via oxygen,which is much more expensive. To force reaction (b) to predominateduring gasification the presence of sufficient moisture is important.

It is obvious that a process that produces a syngas containing arelatively high methane content and therefore a high cold gas efficiencywill be useful in a power application. However, such a syngascomposition may not be the optimum choice for a different syngasapplication in which syngas requires an optimum H₂/CO yield. By varyingthe moisture content in feed stock the syngas production rate andcomposition can be enhanced in order to favor or disfavor one particularapplication. The effect of moisture can have on gasifier performance andsyngas properties also varies according to the characteristics of thefeed stock. For example, the chemically bonded moisture and carboncontent are two parameters that can influence of moisture on the feedstock during gasification. For a high carbon content fuel, such as drycoal, in which chemically bonded moisture is low, increasing themoisture content improves syngas production rate by stimulating reaction(b) above, and improves syngas heating value. In contrast, for feedstock having high chemically bonded moisture, such as wood, furtherincreasing the moisture content results in a lower gasificationefficiency, although it increases the hydrogen production and thus H₂/COratio, by promoting the water-gas shift reaction (reaction (b) above).At lower gasification temperatures the moisture content may alsoincrease methane production which results in a syngas suitable for powergeneration applications. In the presence of moisture at highgasification temperatures, methane production will be reduced.

Thus, the appropriate moisture content in gasification feed stock, likesteam injection into gasifiers, is a useful and economic gasificationmoderator, which can achieve at least one of the following:

(a) Controlling the Gasifier Temperature:

FIG. 5 shows the predicted effect of moisture on gasificationtemperature, carbon conversion and H₂+CO production rate for a typicalcoal feed stock at a constant air equivalence (ER) ratio (ER=0.34).Higher moisture containing feed stock, when gasified, can lower thegasification temperature which allows higher ash content feed stocks tobe gasified. Operation of the gasifier at lower temperatures ispreferred for such engineered fuel feed stocks due to their propensityfor slagging or ash fusion. Presence of moisture in feed stock alsoincreases the conversion of carbon, making low temperature operation ofthe gasification possible while still being capable of reducing thepotential risk of ash slagging, fusion.

(b) Alternating the Syngas Production:

As steam injection is often needed to control the gasificationtemperature, and condition the syngas compositions, particularly methaneproduction and H₂/CO ratio to suit for particular syngas applications(for power generation or chemical synthesis). FIG. 6 shows the predictedvariation of syngas compositions with feed stocks of different moisturecontents for a typical wood feed stock at 800° C.

(c) Increasing Carbon Conversion:

Due to promotion of the water-gas shift reaction (CO+H₂O=CO₂+H₂), higheror complete carbon conversion can be achieved at reduced gasificationtemperatures. This not only allows the lower temperature operation, butalso improves the CO+H₂ production rate, and gasification efficiency.However, when the moisture is too high, the CO+H₂ production rate andcold gas efficiency may decline because of increased combustion (toprovide heat necessary for attaining the same gasification temperature).FIG. 7 shows the predicted effect of fuel moisture content on carbonconversion, cold gas efficiency and CO+H₂ production rate for a typicalcoal feed stock at 850° C. FIG. 8 shows the predicted effect of fuelmoisture content on carbon conversion, cold gas efficiency and CO+H₂production rate for pure carbon at 1000° C.

(d) As an Oxidant:

FIG. 9 shows the predicted total and external water supply required toproduce a syngas of H₂/CO=2.0 at 850° C. for a typical wood feed stock.Moisture in feed stock can replace the external steam supply in casesteam is used as oxidant, which is often the case when external heat isavailable, and/or saving oxygen is desired. By replacing air or oxygenas the oxidant, by water from feed stock, a high BTU syngas can beproduced due to reduced dilution of nitrogen, and increased water-gasreaction (b). In addition to increasing the H₂/CO ratio, the H₂+COproduction rate and cold gas efficiency will be slightly increased withincreasing moisture when operating at a constant gasificationtemperature and air-equivalence ratio (FIG. 8). FIG. 10 shows thepredicted CO+H₂ production rate, cold gas efficiency and H₂/CO ratio at850° C. and an ER=0.30 for a typical wood feed stock.

By judiciously selecting for components of MSW according to, forexample, parameters discussed above, and negatively or positivelyselecting the components from the MSW waste stream, followed by blendingof the components, and optionally any other additives deemed necessary,in the correct proportions, engineered fuel feed stocks can beengineered for a specified use. For example, Table 5 lists some commoncomponents found in MSW, along with their C, H, O, N, S, ash, and HHVcontent, as well as the ER required for complete combustion. Thecomponents can be sorted into any different number of classes, accordingto, for example, their carbon content. For example, MSW can be sortedinto two, three, four, five or even more classes. In one embodiment,Table 5a lists four separate classes; class #1 has a carbon content ofabout 45%, class #2 has a carbon content of about 55%, class #3 has acarbon content of about 60%, and class #4 has a carbon content of about75%.

TABLE 5 Air at Sorted HHV ER = 1 Waste C H O N S A (BTU/lb) (lb/lb) Wood49.5 6 42.7 0.2 0.1 1.5 8,573 5.9 Food waste 48 6.4 37.6 2.6 0.4 5 8,7146.1 Paper 43.5 6 44 0.3 0.2 6 7,595 5.2 Cardboard 44 5.9 44.6 0.3 0.2 57,585 5.2 Yard waste 47.8 6 38 3.4 0.3 4.5 8,387 5.9 Textiles 55 6.631.2 4.6 0.15 2.5 10,093 7.2 Plastics 60 7.2 22.8 0 0 10 11,795 8.4Leather 60 8 11.6 10 0.4 10 12,340 9.1 Rubber 78 10 0 2 0 10 17,154 12.4 

 FOUR CLASSES

TABLE 5A Air at Waste HHV ER = 1 Class C H O N S A (BTU/lb) (lb/lb)Class #1 45.0 6.1 41.4 1.4 0.2 4.4 8171 5.6 Class #2 55.0 6.6 31.2 4.60.2 2.5 10,093 7.2 Class #3 60.0 7. 617.2 5.0 0.2 10.0 12,067 8.7 Class#4 75.0 10.0 0.0 2.0 0.0 10.0 17,154 12.4

In order to engineer a fuel possessing certain specified parameters,equation 1 can be used to select from, and assign the amounts from, thefour classes listed in Table 5a.

                                          eq.  1${f(x)} = \sqrt{\begin{matrix}{{f_{c}\left( {{\sum{x_{i}C_{i}}} - C_{w}} \right)}^{2} + {f_{h}\left( {{\sum{x_{i}H_{i}}} - H_{w}} \right)}^{2} + {f_{o}\left( {{\sum{x_{i}O_{i}}} - O_{w}} \right)}^{2} +} \\{{f_{n}\left( {{\sum{x_{i}N_{i}}} - N_{w}} \right)}^{2} + {f_{z}\left( {{\sum{x_{i}S_{i}}} - S_{w}} \right)}^{2} + {F_{z}\left( {{\sum{x_{i}A_{i}}} - A_{w}} \right)}^{2}}\end{matrix}}$   where   0  << X_(i  )<< 1  and  ∑x_(i) = 1${{\sum\limits_{i = 1}^{n}{x_{i}C_{i}}} + {\sum\limits_{i = 1}^{n}{x_{i}H_{i}}} + {\sum\limits_{i = 1}^{n}{x_{i}S_{i}}} + {\sum\limits_{i = 1}^{n}{x_{i}A_{i\;}}} + {\sum\limits_{i = 1}^{n}{x_{i}O_{i}}} + {\sum\limits_{i = 1}^{n}{x_{i}N_{i}}}} = 100$

For example, an engineered fuel feed stock made from MSW can be designedto have the same chemical composition as natural woodchips. Naturalwoodchips have the chemical composition listed in Table 6. The preciseamounts of the different classes of sorted MSW listed in Table 5 neededfor engineering a synthetic fuel of the same chemical composition asnatural woodchips were determined according to eq. 1 to be 88.1% fromclass #1 and 11.9% from class #2. No components from classes #3 and #4were required for this particular synthetic engineered fuel feed stock.

TABLE 6 HHV Air at Molec- (BTU/ ER = 1 ular Chemical C H O N S A lb)(lb/lb) Weight Formula Engineered 47.6 6.1 40.2 1.7 0.2 4.2 8,400 5.824.2 CH_(1.54)- Fuel O_(0.66)N_(0.031) Simulating Woodchips Woodchips49.5 6.0 42.7 0.2 0.1 1.5 8,573 5.9 23.7 CH_(1.45)- O_(0.63)N_(0.033)

The ultimate and proximate chemical analysis of woodchips and FS#4 aretabulated in Table 7.

TABLE 7 FS #4 Wood 82% Newsprints, 18% Wood pellets Plastics AR MF AR MFMoisture 6.51 3.64 Ash 0.54 0.58 9.62 9.98 Volatile 82.03 87.74 77.2680.18 Fixed Carbon 10.92 11.68 9.48 9.84 S 0 0.01 0.08 0.01 H 5.39 5.775.45 5.66 C 45.58 48.75 41.81 43.39 N 0.01 0.01 0.07 0.07 O 41.98 44.9039.33 40.82 Cl H/C 0.12 0.12 0.13 0.13 O/C 0.92 0.92 0.94 0.94 HHV(BTU/lb) 7,936 8,489 7,296 7,572 HHV (BTU/lb), 8,225 7,520 CalculatedDensity (lb/cu. ft) 41.8 33.7

Gasification tests were performed at a laboratory scale stratifieddowndraft gasifier. The gasifier has an inside diameter of 4 inches anda height of 24 inches above a perforated grate. There are four Type-Kthermocouples installed along the gasifier, 1″, 7″, 19″ above the grateand 4″ below the grate. The real-time temperatures are recorded by adata logger thermometer (OMEGA, HH309A). A syngas sampling train,consisting of two water scrubbers, and a vacuum pump is used for takingsyngas samples, which is analyzed by a HP5890A gas chromotograph toobtain volumetric fractions of H2, N2, CO, CO2 and CH4. A dry gas testmeter is installed in the air entrance to measure the air intake rate.The tests with two wood and simulated wood were conduced with air asoxidant at similar operating conditions. The results are listed in Table8.

TABLE 8 Simulated Wood Parameter Wood (FS#4) H2 20.3 19.8 N2 44.8 46.4CO 24.1 24.7 CH4 2.0 1.2 CO2 8.7 8.0 H2/CO 0.84 0.80 BTU/scf 167.4 159.2

As can be observed in Table 8, the amounts of H₂, N₂, CO, CH₄, CO₂produced from the gasification of woodchips are very similar to thoseproduced from the gasification of feed stock #4. In addition, the ratioof H₂/CO and the BTU/scf is within about 5%. This engineered fuel feedstock demonstrates that by using the methods described herein, feedstocks can be engineered that approximate a natural fuel such as wood.

Fuels of Similar Energy Content do not Necessarily Demonstrate SimilarGasification or Combustion Profiles

However is does not follow that two fuels possessing the same energycontent (for example HHV or BTU/lb) will combust or gasify with the samereactivity or produce the same thermal conversion profile. For example,two feed stocks were prepared containing approximately 14,000 BTU/lb.Feed stock #2 (FS#2) has an energy content of 13,991 BTU/lb and feedstock #7 (FS#7) has an energy content of 14,405 BTU/lb, a difference ofabout 3%. The chemical molecular characteristics of the two feed stocksare listed in Table 9. The moisture content, carbon content, hydrogencontent, oxygen content, and ratios of H/C and O/C are very differentcompared to each other.

TABLE 9 FS#2 FS#7 36% Magazines, 80% Rubber, 20% 64% Plastics Paper +13% water AR MF AR MF Moisture 0.94 13.1 Ash 6.53 6.59 3.84 4.42Volatile 92.48 93.36 61.94 71.28 Fixed Carbon 0.05 0.05 21.12 24.30 S0.05 0.01 1.28 0.01 H 9.51 9.60 5.87 6.75 C 68.85 69.50 75.12 86.44 N0.01 0.01 0.03 0.03 O 14.12 14.25 0.77 0.89 Cl 0.076 0.09 C/H 7.2 7.212.8 12.8 C/O 4.9 4.9 97.6 97.6 HHV (BTU/lb) 13,991 14,124 14,405 16,577HHV (BTU/lb), 15,064 16,574 Calculated Density (lb/cu. ft)

The feed stocks were gasified using the following procedure.Gasification tests were performed at a laboratory scale stratifieddowndraft gasifier. The gasifier has an inside diameter of 4 inches anda height of 24 inches above a perforated grate. There are four Type-Kthermocouples installed along the gasifier, 1″, 7″, 19″ above the grateand 4″ below the grate. The real-time temperatures are recorded by adata logger thermometer (OMEGA, HH309A). A syngas sampling train,consisting of two water scrubbers, and a vacuum pump is used for takingsyngas samples, which is analyzed by a HP5890A gas chromotograph toobtain volumetric fractions of H₂, N₂, CO, CO₂ and CH₄. A dry gas testmeter is installed in the air entrance to measure the air intake rate.The tests with two wood and simulated wood were conduced with air asoxidant at similar operating conditions. The results are listed in thefollowing table. It can be seen that syngas composition, H₂/CO ratio andsyngas HHV are fairly close between the two engineered fuel feed stocks.The results of the gasification of feed stocks FS#2 and FS#7 are listedin Table 10.

TABLE 10 Parameter FS#2 FS#7 Difference % H₂ % 21.9 28.6 30.4 N₂ % 45.645.2 0.8 CO % 18.9 15.6 17.2 CH₄ % 6.4 2.7 57.3 CO₂ % 7.3 7.9 8.6 H₂/CO1.16 1.83 57.4 Syngas HHV (BTU/scf) 200.21 173.8 13.2 CO + H₂ % 40.844.2 8.4

From the data in Table 10, it can be seen that although the two fuelshave very similar energy content (a difference of only about 3%), thedifference in syngas composition is very different. There is a greaterthan 30% difference in H₂ vol. % and CH₄ vol. % and an over 50%difference in the ratio of H₂/CO between the two feed stocks, whichmeans that the synthesis gases from these two fuels could not be usedfor the production of similar Fischer-Tropsch fuels. There is a 13%difference in the energy content of the synthesis gas and a 17%difference in the amount of CO produced between the two feed stocks.This experiment demonstrates that consideration of only the BTU/lb valueof feed stocks does not give a true indication of what type of syngasprofile the feed stock will have.

Combustion

The same calculation was performed on theoretical feed stocks except thecondition were under combustion rather than gasification. All feedstocks were assumed to have the same HHV of 10,000 BTU/lb, and thenchanges to the combinations of carbon content, hydrogen content, oxygencontent, ash content and moisture content were introduced. The resultsare tabulated in Table 11.

TABLE 11 # 1 # 2 # 3 # 4 # 5 BTU Value/lb 10,000 10,000 10,000 10,00010,000 Moisture 5 5 5 5 5 Ash 5 5 5 5 5 S 0.1 0.1 0.1 0.1 0.1 H 1 3.310.1 6.9 3.7 0.5 C 30 40 50 60 70 N 0.1 0.1 0.1 0.1 0.1 O 46.6 39.7 32.926.1 19.3 C/H 2.3 4.0 7.3 16.4 147.3 C/O 0.6 1.0 1.5 2.3 3.6 Stoich. Air(scf/lb) 78.8 83.2 87.7 92.2 96.7 Combustion Products Excess Air Ratio28.5% 29.5% 30.0% 31.0% 32.0% O2 (scf/lb) 4.7 5.2 5.5 6.0 6.5 N2(scf/lb) 80.0 85.2 90.1 95.4 100.8 CO2 (scf/lb) 9.5 12.7 15.8 19.0 22.1H2O (scf/lb) 26.2 20.1 14.1 8.0 2.0 SO2 (scf/lb) 0.012 0.012 0.012 0.0120.012 Total (scf/lb) 120.4 123.1 125.5 128.4 131.4 Flue Gas (dry %) O2(dry vol. %) 5.0 5.0 5.0 5.0 5.0 N2 (dry vol. %) 84.9 82.7 80.8 79.277.9 CO2 (dry vol. %) 10.1 12.3 14.2 15.8 17.1 SO2 (dry, ppmv) 126 115106 99 92

As can be seen in Table 11, theoretical feed stocks #1 to #5 all havethe same HHV of 10,000 BTU/lb, but the carbon content varies from 30% to70% (H and O will also vary accordingly). From the numbers listed thestoichiometric air requirement for complete combustion varies from 78.8to 96.7 scf per lb of feed stock. Due to this difference, combustionproducts will vary, and noticeably the excess air ratio must be adjustedin actual combustion operation if the operator is monitoring stack O₂.In the above calculations, excess air has to be adjusted from 28.5% forfeed stock #1 to 32% for feed stock #5 if the target O₂ in stack is at5%.

TABLE 12 BTU Value/lb #3 #8 #9 #10 Moisture 5 10 15 20 Ash 5 5 5 5 S 0.10.1 0.1 0.1 H 6.9 5.6 4.4 3.2 C 50 50 50 50 N 0.1 0.1 0.1 0.1 O 32.929.2 25.4 21.6 C/H 7.3 8.9 11.3 15.6 C/O 1.5 1.7 2.0 2.3 Stoich. Air87.7 84.3 81.0 77.6 (scf/lb) Combustion Products Excess Air Ratio 30.0%30.5% 31.0% 31.0% O2 (scf/lb) 5.5 5.4 5.3 5.0 N2 (scf/lb) 90.1 86.9 83.880.3 CO2 (scf/lb) 15.8 15.8 15.8 15.8 H2O (scf/lb) 14.1 12.8 11.6 10.3SO2 (scf/lb) 0.012 0.012 0.012 0.012 Total (scf/lb) 125.5 121.0 116.4111.4 Flue Gas (dry %) O2 (dry vol. %) 5.0 5.0 5.0 5.0 N2 (dry vol. %)80.8 80.4 79.9 79.4 CO2 (dry vol. %) 14.2 14.6 15.1 15.6 SO2 (dry, ppmv)106 110 113 117

In Table 12 the theoretical feed stocks each have an energy value of10,000 BTU/lb but the moisture content was varied from between 5% to20%. The stoichiometric air requirement for complete combustion variesfrom 87.7 for #3 (5% moisture) to 77.6 for #10 (20% moisture) scf per lbof feed stock. Thus, for combustion operation, consideration of only theBTU content of a feed stock is insufficient to know what the combustionprofile will be. Feed stocks possessing the same BTU value but differentchemical molecular characteristics will exhibit different combustionbehavior and require different combustion controls. It is alsoanticipated that the combustor temperature will also vary even with feedstocks containing the same BTU value yet having different chemicalmolecular characteristics.

Design of High BTU Fuels

To design the maximum BTU containing fuel while minimizing the risk ofslagging, a limit on the amount of ash present must be taken intoaccount. For biomass fuels, it has been reported that fuels comprisingless than about 5% ash appear not to slag as much as fuels containingmore than about 5% ash (see Reed, T. B., and A. Das, Handbook of BiomassDowndraft Gasifier Engine Systems. Golden: SERI, 1988). Ashes can causea variety of problems particularly in up or downdraft gasifiers.Slagging or clinker formation in the reactor, caused by melting andagglomeration of ashes, at the best will greatly add to the amount oflabor required to operate the gasifier. If no special measures aretaken, slagging can lead to excessive tar formation and/or completeblocking of the reactor.

Whether or not slagging occurs depends on the ash content of the fuel,the melting characteristics of the ash, and the temperature pattern inthe gasifier. Local high temperatures in voids in the fuel bed in theoxidation zone, caused by bridging in the bed and maldistribution ofgaseous and solids flows, may cause slagging even using fuels with ahigh ash melting temperature. In general, no slagging is observed withfuels having ash contents below 5-6 percent. Severe slagging can beexpected for fuels having ash contents of 12 percent and above. Forfuels with ash contents between 6 and 12 percent, the slagging behaviordepends to a large extent on the ash melting temperature, which isinfluenced by the presence of trace elements giving rise to theformation of low melting point eutectic mixtures. Equation 2 below givesthe relationship between the energy content of the fuel (HHV) and theamount of ash contained in the engineered fuel feed stock.

$\begin{matrix}{\mspace{79mu} {Maximize}} & \; \\{{{HHV}_{fuel} = {{146.4{\sum\limits_{i = 1}^{n}{x_{i}C_{i}}}} + {588.8{\sum\limits_{i = 1}^{n}{x_{i}H_{i}}}} + {29.4{\sum\limits_{i = 1}^{n}{x_{i}S_{i}}}} - {6.6{\sum\limits_{o = 2}^{n}{x_{i}A_{i\;}}}} - {51.5\left( {{\sum\limits_{i = 1}^{n}{x_{i}O_{i}}} + {\sum\limits_{i = 1}^{n}{x_{i}N_{i}}}} \right)}}}\mspace{20mu} {{\sum\limits_{i = 1}^{n}{x_{i}A_{i}}} < {5\mspace{14mu} \left( {{to}\mspace{14mu} {minimize}\mspace{14mu} {risk}\mspace{14mu} {of}\mspace{14mu} {slagging}} \right)}}\mspace{20mu} {\sum\limits_{i = 1}^{n}{x_{i}S_{i}\mspace{14mu} \left( {{less}\mspace{14mu} {than}\mspace{14mu} a{\mspace{11mu} \;}{predetermined}\mspace{14mu} {value}} \right)}}{{\sum\limits_{i = 1}^{n}{x_{i}C_{i}}} + {\sum\limits_{i = 1}^{n}{x_{i}H_{i}}} + {\sum\limits_{i = 1}^{n}{x_{i}S_{i}}} + {\sum\limits_{i = 1}^{n}{x_{i}A_{i\;}}} + {\sum\limits_{i = 1}^{n}X_{i}} + O_{i} + {\sum\limits_{i = 1}^{n}{x_{i}N_{i}}} + 100}} & {{eq}.\mspace{14mu} 2}\end{matrix}$

By use of the above equations an engineered fuel feed stock with a HHVof about 10,000 BTU/lb can be designed whereby the ash is held to aminimum amount, for example, less than about 5% ash, or less than about4% ash. The components of MSW used to engineer the fuels of about 10,000BTU/lb were selected from the four classes of MSW components derivedfrom MSW listed in Table 5. Table 13 lists the amounts of the componentsof MSW used for engineering these fuels and their corresponding carbon,hydrogen, sulfur, and ash contents as well as the HHV value for theengineered fuel.

TABLE 13 HHV C II O N S Ash (BTU/lb) Ash content < 4% 56.0 6.8 28.4 4.60.2 4.0 10,493 (80% Class #2, 20% Class #3) Ash content < 5% 56.7 6.926.5 4.7 0.2 5.0 10,756 (67% Class #2, 33% Class #3)

Design of Engineered Fuel Feed Stock Based on Target Syngas Compositionfor Downstream Fischer-Tropsch Chemistry

In some embodiments, during production of the densified form of theengineered fuel feed stock, it is determined that the chemical molecularcharacteristic of the densified form is lower than that required for aparticular gasifier, the amount of other materials that enhance thegasification process may be increased during the process therebybringing the chemical molecular characteristics of the densified form ofthe engineered fuel feed stock within the desired fuel specification. Inother embodiments, other materials that enhance the gasification processmay be added before or during the compression to adjust the chemicalmolecular characteristics of the resulting densified form of theengineered fuel feed stock. In some embodiments the other material addedto the feed stock is a FOG. Table 16 lists the heat content of certainFOGs and their carbon and hydrogen contents.

TABLE 16 Type of FOG BTU/lb Carbon Content Hydrogen Content Tallow16,920 76.6% 11.9% Chicken Fat 16,873 75.3% 11.4% Yellow Grease 16,89976.4% 11.6% Choice White Grease 16,893 76.5% 11.5% Waste Motor Oil16,900 Not available Not available

Another type of material that can be added to the feed stock is sludge.Table 17 gives the carbon and hydrogen content of sludge.

TABLE 17 Elemental Analysis Primary Secondary Mixed Digested Carbon 60.053.0 57.0 67.0 Hydrogen 7.5 7.0 7.0 5.0 Oxygen 28.0 30.5 30.0 25.0Nitrogen 3.0 9.0 5.0 2.2 Sulfur 1.5 0.5 1.0 0.8 Total 100 100 100 100

The best-known technology for producing hydrocarbons from synthesis gasis the Fischer-Tropsch synthesis. This technology was first demonstratedin Germany in 1902 by Sabatier and Senderens when they hydrogenatedcarbon monoxide (CO) to methane, using a nickel catalyst. In 1926Fischer and Tropsch were awarded a patent for the discovery of acatalytic technique to convert synthesis gas to liquid hydrocarbonssimilar to petroleum.

The basic reactions in the Fischer-Tropsch synthesis are:

Paraffins:

(2n+1)H₂ +nCO→C_(n)H_(2n+2) +nH₂O

Olefins:

2nH2+nCO→C_(n)H_(2b) +nH₂O

Alcohols:

2nH₂ +nCO→C_(n)H_(2n+1)OH+(n−1)H₂O

Other reactions may also occur during the Fischer-Tropsch synthesis,depending on the catalyst employed and the conditions used:

Water-gas shift:

CO+H₂O→CO₂+H₂

Boudouard disproportionation:

2CO→C(s)+CO₂

Surface carbonaceous deposition:

$\left. {{\left( \frac{{2x} + y}{2} \right)H_{2}} + {x\; {CO}}}\rightarrow{{C_{x}H_{y}} + {x\; H_{2}O}} \right.$

Catalyst oxidation-reduction:

yH2O+xM→M_(x)O_(y) +yH2

yCO2+xM→M_(x)O_(y) +yCO

Bulk carbide formation:

yC+xM→M_(x)C_(y)

where M represents a catalytic metal atom.

The production of hydrocarbons using traditional Fischer-Tropschcatalysts is governed by chain growth or polymerization kinetics.Equation 3 describes the production of hydrocarbons, commonly referredto as the Anderson-Schulz-Flory equation.

$\begin{matrix}{{\log \left( \frac{W_{2}}{n} \right)} + {\log \; \alpha}\; + {\log\left\lbrack \frac{\left( {1 - \alpha} \right)^{2}}{\partial} \right\rbrack}} & {{eq}.\mspace{14mu} 3}\end{matrix}$

where W_(n)=weight fraction of products with carbon number n, andα=chain growth probability, i.e., the probability that a carbon chain onthe catalyst surface will grow by adding another carbon atom rather thanterminating. In general, α is dependent on concentrations or partialpressures of CO and H2, temperature, pressure, and catalyst compositionbut independent of chain length. As a increases, the average carbonnumber of the product also increases. When α equals 0, only methane isformed. As a approaches 1, the product becomes predominantly wax.

FIG. 11 provides a graphical representation of eq. 2 showing the weightfraction of various products as a function of the chain growth parameterα. FIG. 11 shows that there is a particular a that will maximize theyield of a desired product, such as gasoline or diesel fuel. The weightfraction of material between carbon numbers m and n, inclusive, is givenby equation 4:

W _(mn) =mα ^(m-1)−(m−1)α^(m)−(n+1)α^(n) +nα ^(n+1)  (eq. 4)

The α to maximize the yield of the carbon number range from m to n isgiven by equation 5.

$\begin{matrix}{\alpha_{opt} = \left( \frac{m_{2}m}{n_{2} + n} \right)^{\frac{1}{n - m + 1}}} & \left( {{eq}.\mspace{14mu} 5} \right)\end{matrix}$

Additional gasoline and diesel fuel can be produced through furtherrefining, such as hydrocracking or catalytic cracking of the waxproduct.

For each of the targeted products derived from syngas the correspondingappropriate H₂/CO ratio is needed. One way to produce such H₂/CO ratiois to control the amount of C, H, and O in the feed stock used toproduce the syngas. For example, FIG. 12 shows the predicted C/H and C/Oratios needed in the feed stock in order to produce a syngas of therequisite H₂/CO ratio.

TABLE 14 H₂/CO Product Basic Chemical Reaction Ratio FT Liquid 2nH₂ +nCO → C_(n)H_(2n) + nH₂O; 2:0-2.1 fuels (2n + 1)H₂ + nCO →C_(n)H_(2n+1) + nH₂O Methanol 2H₂ + CO═CH₃OH; CO₂ + 3H₂ → 2.0 CH₃OH +H₂O Ethanol 2CO + 4H₂ → C₂H₅OH + H₂O 2.0 Higher nCO + 2nH₂ →C_(n)H_(2n+1)OH + (n − 1) H₂O 2.0 alcohols Dimethyl 2CO + 4H₂ →CH₃OCH₃ + H₂O 2.0 ether Acetic Acid 2CO + 2H₂ → CH₃COOH 1.0 Ethylene2CO + 4H₂ → C₂H₄ + 2H₂O 2.0 Ethylene 2CO + 3H₂ → C₂H₆O₂ 1.5 Glycol Ac₂O4CO + 4H₂ → (CH₃CO)₂O + H₂O 1.0 Ethyl Acetate 4CO + 6H₂ → CH₃COOC₂H₅ + 2H₂O 1.50 Vinyl Acetate 4CO + 5H₂ → CH₃COOCH═CH₂ + 2 H₂O 1.25

By first selecting the H₂/CO ratio desired in the product syngas, theproper ratio of H/C and O/C in the composition of the engineered feedstock can be determined, along with the proper amount of moisture andash content. Once these ratios have been determined then the proper MSWcomponents can be selected and combined together to form feed stocksthat upon gasification will yield a syngas with the desired H₂/CO ratio.

Physical Properties that Affect Efficient Gasification or Combustion ofFuel Particles

Up and downdraft gasifiers are limited in the range of fuel sizeacceptable in the feed stock. Fine grained and/or fluffy feed stock maycause flow problems in the bunker section of the gasifier as well as aninadmissible pressure drop over the reduction zone and a high proportionof dust in the gas. Large pressure drops will lead to reduction of thegas load of downdraft equipment, resulting in low temperatures and tarproduction. Excessively large sizes of particles or pieces give rise toreduced reactivity of the fuel, resulting in startup problems and poorgas quality, and to transport problems through the equipment. A largerange in size distribution of the feed stock will generally aggravatethe above phenomena. Too large particle sizes can cause gas channelingproblems, especially in updraft gasifiers. Acceptable fuel sizes foxgasification systems depend to a certain extent on the design of theunits.

Particle size distribution in fuel influences aspects of combustor andgasifier operations including the rate at which fuel reacts with oxygenand other gases. Smaller particles of fuel tend to be consumed fasterthan bigger ones. Particle size is based on area-volume average (d_(pv))(eq. 6). The distribution of particle sizes in a population of particlesis given by d_(pv) (eq. 7):

$\begin{matrix}{d_{p} = \left( \frac{6\; V_{p}}{\pi} \right)} & \left( {{eq}.\mspace{14mu} 6} \right) \\{d_{p} = \frac{1}{\sum\limits_{i = 1}^{n}\frac{w_{i}}{d_{{pv}\; \cdot 1}}}} & \left( {{eq}.\mspace{14mu} 7} \right)\end{matrix}$

The shape of the engineered fuel feed stock particles and the densifiedform of the engineered fuel feed stock also strongly influence the ratesof gas-solid reactions and momentum transfers between the particles andthe gas stream that carries them. One parameter used to describe theshape of a particle is sphericity, which affects the fluidity of theparticles during the gasification/combustion process. Fluidity isimportant in avoiding channeling and bridging by the particles in thegasifier, thereby reducing the efficiency of the conversion process.Sphericity can be defined by the following formula:

${\phi \; p} = \frac{{Surface}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {spherical}\mspace{11mu} {particle}}{\mspace{14mu} \begin{matrix}{{Surfa}\; {ce}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {particle}\mspace{14mu} {with}} \\{{same}\mspace{14mu} {volume}\mspace{14mu} {of}\mspace{14mu} {the}\mspace{14mu} {spherical}\mspace{14mu} {one}}\end{matrix}}$

Particle size, d_(pv), and sphericity, φ_(p) together in therelationship φ_(p)•d_(pv), influence hydrodynamic characteristics ofparticles while in a combustor or gasifier. These hydrodynamiccharacteristics include among others pressure drop, minimum fluidizationvelocity, terminal velocity and momentum transfer. By way of example,particles of coal, limestone, and sand, present with sphericity thatranges from 0.6 to 0.9. Woodchips particles, for example, present with asphericity of about O₂.

The rates of gas-solids reactions depend on the available surface areaof the particle. Therefore, for particles of similar volumes, theparticle with the higher surface area will be consumed faster and moreefficiently and therefore effect the gasification process. Equations 8and 9 describe the volume of a sphere and cylinder, respectively.

$\begin{matrix}{{d_{p} = {\frac{S_{p}}{V_{p}} = \frac{6}{d_{pv}}}};} & \left( {{eq}.\mspace{14mu} 8} \right) \\{\alpha_{p} = {\frac{S_{p}}{V_{p}} = \frac{{2\frac{1}{4}\pi \; d^{2}} + {\pi \; {dh}}}{\frac{1}{4}\pi \; d^{2}h}}} & \left( {{eq}.\mspace{14mu} 9} \right)\end{matrix}$

Table 15 below lists different cylinders and a sphere that all have thesame volume (0.524 in³), yet possessing different surface areas (in²)and specific surface areas (in²/in³).

TABLE 15 Specific Characteristic Average Surface Volume surfacedimensions diameter area (in²) (in³) area (in²/(in³) Sphericity Sphereφ1″ φ1″ 3.142 0.524 6.0 1 Cylindrical  φ0.5″ × 2.667″ φ1″ 4.518 4.5188.75 0.686 Cylindrical  0.87″ × 0.88″  φ1″ 3.596 3.596 6.87 0.874Cylindrical  φ1.0″ × 0.667″ φ1″ 3.665 3.665 7.0 0.857 Cylindrical φ11.5″× 0.296″ φ1″ 4.931 4.931 9.471 0.637

For shapes with the same volume such as cylinders and spheres, sphereshave the lowest specific surface area. As the sphericity of a cylinderapproaches 1 it behaves more like a sphere in thegasification/combustion process. However, the surface area for thecorresponding volume is not maximized in the shape of a sphere whichmeans the conversion process will not be optimally efficient. There is aminimum specific surface area and highest sphericity for a cylindricalshape depending on its diameter and length. This shape when determinedfor the engineered fuel is optimal for the conversion process for whichthe fuel is used. FIG. 13 shows that when the cylindrical diameter isplotted against the sphericity and the cylindrical length and specificarea, the optimal size of the pellet can be determined.

For a given equivalent diameter, (FIG. 13), there is a minimum inspecific surface area corresponding to a maximum sphericity when thecylindrical diameter almost equals its length. Away from this point, thesphericity decreases but the specific surface area increases which meansthat while the fluidity is declining, the rates of gas-solid reactionsbecomes favored. The optimal pellet dimensions have a maximum possiblespecific surface area while maintaining a sphericity value high enoughto ensure excellent fluidity. This parameter minimizes or even preventsbridging and channeling of pellets inside the gasifiers, which decreasesthe efficiency of the conversion process.

As described above, the engineered feed stock should provide maximumsurface area for the same volume in order to favor gas-solid reactionswhich is determined by maximization of αp in eq. 10.

$\begin{matrix}{{{maximize}\mspace{14mu} \alpha_{p}} = \frac{{2\frac{1}{4}\pi \; d^{2}} + {\pi \; d\; h}}{\frac{1}{4}\pi \; d^{2}h}} & \left( {{eq}.\mspace{14mu} 10} \right)\end{matrix}$

The maximization of αp for a particular feed stock provides betterhydrodynamic performance during the conversion process and costeffectiveness in preparation (size reduction and pelletizing) of theengineered fuel as compared to other natural fuels.

For further optimization of combustion or gasification performance, thesize and shape, and in some embodiments, the sphericity, of theengineered fuel feed stock can be determined. For example, to engineer afuel having a densified form that will produce similar results ascompared with, for example, natural woodchips in gasification andcombustion processes, the sphericity of natural woodchips provides anatural starting point. Natural woodchips have a sphericity (φ_(p)) ofabout 0.2. An engineered fuel particle was designed with a sphericity of0.25, a slightly better sphericity than natural woodchips yet containingthe same HHV. Equation 11 describes the size of the engineered fuelparticle and Table 18 lists the possible dimensions for such anengineered particle:

$\begin{matrix}{{\varphi_{p} = {\frac{\pi \left( {6\; {V_{p}/\pi}} \right)}{S_{p}} \geq {a\mspace{14mu} {predetermined}\mspace{14mu} {value}}}}{{\varphi_{p}d_{pv}} \geq {a\mspace{14mu} {predetermined}\mspace{14mu} {value}}}} & \left( {{eq}.\mspace{14mu} 11} \right)\end{matrix}$

TABLE 18 Overall particle size (in) 1.0 1.5 2.0 Diameter (in) 0.83 1.351.91 Length (in) 1.67 1.93 2.21 Specific Surface Area (ft²/ft³) 72 48 36

From the values shown in Table 18, the smallest particle actually hasthe greatest specific surface area (72 ft²/ft³ versus 48 ft²/ft³ and 36ft²/ft³, respectively).

The rate of gasification of the fuel pellets can be positively effectedby a number of elements which act as catalysts, such as small quantitiesof potassium, sodium or zinc.

Bulk density is defined as the weight per unit volume of loosely tippedfuel. Fuels with high bulk density are advantageous because theyrepresent a high energy-for-volume value. Low bulk density fuelssometimes give rise to insufficient flow under gravity, resulting in lowgas heating values and ultimately in burning of the char in thereduction zone. Average bulk densities of solid fuels such as wood, coaland peat ranges from about 10 lb/ft³ to about 30 lb/ft³. If bulkdensities for some components used for the pellets of the invention aretoo low, the over all bulk density can be improved throughpelletization. The bulk density varies significantly with moisturecontent and particle size of the fuel.

Exemplary ranges for specifications of a waste feed for a gasificationsystem can include, but are not limited to: a diameter of between about0.25 inches to about 1.5 inches; a length of between about 0.5 inch toabout 6 inches; a surface to volume ratio of between about 20:1 to about3:1; a bulk density of about 10 lb/ft³ to about 75 lb/ft³; a porosity ofbetween about 0.2 and about 0.6; an aspect ratio of between about Itoabout 10; a thermal conductivity of between about 0.023 BTU/(ft·hr·° F.)and about 0.578 BTU/(ft·hr·° F.); a specific heat capacity of betweenabout 4.78×10⁻⁵ to 4.78×10⁻⁴ BTU/(lb·° F.); a thermal diffusivity ofbetween about 1.08×10⁻⁵ ft²/s to 2.16×10⁻⁵ ft²/s; a HHV of between about3,000 BTU/lb to about 15,000 BTU/lb; a moisture content of about 10% toabout 30%; a volatile matter content of between about 40% to about 80%;a carbon content of between about 30% to about 80%; a hydrogen contentof between about 3% to about 10%, a sulfur content of less than 2%; achlorine content of less than 1%; and an ash content of less than about10%.

From the results show in FIG. 14, MSW feed stock can be classifiedaccording to its carbon content and thus its potential for producing theamount of CO and H₂ in the resulting syngas upon thermal conversion.Table 19 shows one classification of types of fuels based on carboncontent: low heat fuels (less than 45 wt % carbon); moderate heat fuels(45-60 wt % carbon); and high heat fuels (>60 wt % carbon).

TABLE 19 Moderate Heat Low Heat Fuels Fuels High Heat Fuels Carboncontent <45 wt % 45-60 wt % >60 wt % H₂ + CO Product <10 scf/lbs 10-20scf/lbs >20 scf/lbs Air Equivalence ratio >0.35 0.1-0.35 <0.1 Syngas HHV(dry basis) <120 BTU/scf 120-200 BTU/scf >200 BTU/scf Gasifiertemperature <850° C. 800-900° C. >900° C. Performance Incomplete CComplete carbon Complete carbon conversion, conversion, minimalconversion, no formation of CH4 formation of CH4 formation of CH₄ andtars and tars, low risk of and tars, high risk slagging of slaggingApplications Syngas for Syngas for all power, Syngas for all combustionliquid fuel and power, liquid fuel applications chemicals and chemicals(engines), co- applications applications gasification w/ other fuelsincluding moderate and high heat fuels as well as LFG

The low heat fuels can be characterized as producing syngas containingCO and H₂ at less than about 10 scf/lbs and an HHV of less than about120 BTU/scf. Because the gasifier requires an air equivalence ratio ofmore than 0.35 because of the low amount of carbon, the gasifiertemperature will not rise above about 850° C. causing incompleteconversion of carbon and the formation of methane and tars. These fuelscan be used for production of syngas for all purposes, co-gasificationwith other fuels including moderate and high heat fuels, as well as LFG.

The moderate heat fuels can be characterized as producing syngascontaining CO and H₂ at about 10 to about 20 scf/lbs and an HHV of about120 to about 200 BTU/scf. Because the gasifier requires an airequivalence ratio of about 0.1 to about 0.35 with a carbon content ofabout 45 wt % to about 60 wt %, the gasifier maintains a temperature ofabout 850° C. to about 900° C. causing complete conversion of carbon,minimal formation of methane and tars, and low risk of slagging. Thesefuels can be used for production of syngas for all applications, liquidfuels, and chemicals applications.

The high heat fuels can be characterized as producing syngas containingCO and H₂ at greater than about 20 scf/lbs and an HHV of greater than200 BTU/scf. Because the gasifier requires an air equivalence ratio ofonly less than about 0.1 with a carbon content of greater than about 60wt %, the gasifier's temperature is generally greater than about 900° C.causing complete conversion of carbon, no formation of methane and tars,but a high risk of slagging. These fuels can be used for production ofsyngas for all applications, liquid fuels, and chemicals applications.

Therefore depending on the end use of the syngas to be produced,engineered fuel feed stocks of different carbon content can be selectedand fuels can be engineered and synthesized for a particular end use.Such selection allows the fine tuning of the engineered fuels producedfrom differing heterogeneous feed stocks such as MSW, FOGS, sludges,etc. The engineered fuels can be used for producing syngas containingthe desired CO and H₂Content.

The MSW can be processed by any method that allows for identificationand separation of the component parts according to material type, suchas by plastics, fibers, textiles, paper in all its forms, cardboard,rubber, yard waste, food waste, and leather. Methods of separation suchas those disclosed in U.S. Pat. No. 7,431,156, US 2006/0254957, US2008/0290006, US 2008/0237093, the disclosures of which are herebyincorporated in their entirety, can be used for separating thecomponents of waste.

It is understood that modifications may be made to the methods ofseparation disclosed above that allow for the recovery of the individualcomponents of MSW for use in engineering engineered fuel feed stock asdescribed herein.

In some embodiments, the component or components of the engineered feedstock are mixed. In some of the embodiments, the mixed components arereduced in size using known techniques such as shredding, grinding,crumbling and the like. Methods for the reduction in size of MSWcomponents is well known and for example are described in U.S. Pat. No.5,888,256, the disclosure of which is incorporated by reference in itsentirety. In other embodiments, the individual components are firstreduced in size prior to mixing with other components. In someembodiments, the mixed components of the engineered fuel feed stock aredensified using known densification methods such as, for example, thosedescribed in U.S. Pat. No. 5,916,826, the disclosure of which isincorporated by reference in its entirety. In some embodiments, thedensification forms pellets by the use of a pelletizer, such as aPasadena hand press, capable of exerting up to 40,000 force-pounds.

In some embodiments, the FOGS component is added directly to the mixingtank. In other embodiments, the FOGS component is added after mixingjust before the waste is placed into a pelletizing die.

By use of a pelletizer under appropriate conditions, pellets areproduced having a range of dimensions. The pellets should have adiameter of at least about 0.25 inch, and especially in the range ofabout 0.25 inches to about 1.5 inches. The pellets should have a lengthof at least about 0.5 inch, and especially in the range of about 0.5inches to about 6 inches.

By selection of the appropriate die to be used with the pelletizer, thepellets become scored on the surface of the encapsulation. This scoringmay act as an identifying mark. The scoring can also affect thedevolatization process such that the scored pellets volatize at a moreefficient rate than the unscored pellets.

In some embodiments, the engineered fuel feed stock described herein isbiologically, chemically and toxicologically inert. The termbiologically inert, chemically inert, and toxicologically inert meansthat the engineered fuel feed stock described herein does not exceed theEPA's limits for acceptable limits on biological, chemical andtoxicological agents contained within the engineered fuel feed stock.The terms also include the meaning that the engineered fuel feed stockdoes not release toxic products after production or upon prolongedstorage. The engineered fuel feed stock does not contain, for examplepathogens or live organisms, nor contain the conditions that wouldpromote the growth of organisms after production or upon prolongedstorage. For example, the engineered fuel feed stock in any formdescribed herein can be designed so as to have a moisture contentsufficient so as not to promote growth of organisms. The engineered fuelfeed stock can be designed to be anti-absorbent, meaning it will notabsorb water to any appreciable amount after production and uponprolonged storage. The engineered fuel feed stock is also air stable,meaning it will not decompose in the presence of air to give offappreciable amounts of volatile organic compounds. The engineered fuelfeed stock described herein may be tested according to known methods inorder to determine whether they meet the limits allowed for thedefinition of inert. For example, 40 CFR Parts 239 through 259promulgated under Title 40—Protection of the Environment, contains allof the EPA's regulations governing the regulations for solid waste. TheEPA publication SW-846, entitled Test Methods for Evaluating SolidWaste, Physical/Chemical Methods, is OSW's official compendium ofanalytical and sampling methods that have been evaluated and approvedfor use in complying with 40 CFR Parts 239 through 259, in relation tosolid waste, which is incorporated by reference herein in its entirety.

EXAMPLES

Reference will now be made to specific examples some of which illustratethe invention. It is to be understood that the examples are provided toillustrate preferred embodiments and that no limitation to the scope ofthe invention is intended thereby.

General Synthetic Procedures

After components for the engineered feed stock were selected they wereshredded in a low speed shredder and then mixed mechanically. Afterwardsthe mixture was densified using a pelletizer. If the moisture contentneeded to be increased, water was added during the mixing step. A smallsample of the feed stock was taken and dried in an temperaturecontrolled and vented oven to confirm the moisture content. The mixedengineered feed stock was then subjected to gasification as describedabove.

Feed Stock Wood (Control)

Wood Wood pellets AR MF Moisture 6.51 Ash 0.54 0.58 Volatile 82.03 87.74Fixed Carbon 10.92 11.68 S 0 0.01 H 5.39 5.77 C 45.58 48.75 N 0.01 0.01O 41.98 44.90 Cl C/H 8.5 8.5 C/O 1.1 1.1 HHV (BTU/lb) 7,936 8,489 HHV(BTU/lb), Calculated 8,225 Density (lb/cu. ft) 41.8

Feed Stock #1

Feed stock #1 (FS#1) 82% Newsprints, 18% Plastics AR MF Moisture 3.25Ash 4.51 4.66 Volatile 86.43 89.33 Fixed Carbon 5.81 6.01 S 0 0.01 H7.57 7.82 C 51.88 53.62 N 0.06 0.06 O 32.65 33.75 Cl C/H 6.9 6.9 C/O 1.61.6 HHV (BTU/lb) 9,552 9,873 HHV (BTU/lb), Calculated 10,696 Density(lb/cu. ft) 20.3

Feed Stock #1 Gasifier Output

Hydrogen, vol % 14.9 Nitrogen, vol % 51.6 Carbon Monoxide, vol % 18.9Methane, vol % 2.3 Carbon Dioxide, vol % 12.3 Hydrogen/Carbon Monoxide0.79 BTU/scf 134.79 Carbon Monoxide + Hydrogen 33.8

Feed Stock #2

FS#2 36% Magazines, 64% Plastics AR MF Moisture 0.94 Ash 6.53 6.59Volatile 92.48 93.36 Fixed Carbon 0.05 0.05 S 0.05 0.01 H 9.51 9.60 C68.85 69.50 N 0.01 0.01 O 14.12 14.25 Cl C/H 7.2 7.2 C/O 4.9 4.9 HHV(BTU/lb) 13,991 14,124 HHV (BTU/lb), Calculated 15,064 Density (lb/cu.ft)

Feed Stock #2 Gasifier Output

Hydrogen, vol % 21.9 Nitrogen, vol % 45.6 Carbon Monoxide, vol % 18.9Methane, vol % 6.4 Carbon Dioxide, vol % 7.3 Hydrogen/Carbon Monoxide1.16 BTU/scf 200.21 Carbon Monoxide + Hydrogen 40.8

Feed Stock #3

FS#3 24.5% Other Papers, 75.5% Textiles AR MF Moisture 1.57 Ash 7.577.69 Volatile 75.12 76.32 Fixed Carbon 15.74 15.99 S 0.37 0.01 H 5.855.94 C 48.12 48.89 N 8.38 8.51 O 28.14 28.59 Cl 3.44 3.49 C/H 8.2 8.2C/O 1.7 1.7 HHV (BTU/lb) 9,629 9,783 HHV (BTU/lb), Calculated 8,705Density (lb/cu. ft) 21.9

Feed Stock #3 Gasifier Output

Hydrogen, vol % 6.5 Nitrogen, vol % 64.6 Carbon Monoxide, vol % 19.3Methane, vol % 0.3 Carbon Dioxide, vol % 9.3 Hydrogen/Carbon Monoxide0.3 BTU/scf 88.6 Carbon Monoxide + Hydrogen 25.7

Feed Stock #4

FS#4 91.8% Newsprint, 2.2% Plastics, 6.0% Yard wastes AR MF Moisture3.64 Ash 9.62 9.98 Volatile 77.26 80.18 Fixed Carbon 9.48 9.84 S 0.080.01 H 5.45 5.66 C 41.81 43.39 N 0.07 0.07 O 39.33 40.82 Cl C/H 7.7 7.7C/O 1.1 1.1 HHV (BTU/lb) 7,296 7,572 HHV (BTU/lb), Calculated 7,520Density (lb/cu. ft) 33.7

Feed Stock #4 Gasifier Output

Hydrogen, vol % 19.8 Nitrogen, vol % 46.4 Carbon Monoxide, vol % 24.7Methane, vol % 1.2 Carbon Dioxide, vol % 8.0 Hydrogen/Carbon Monoxide0.80 BTU/scf 159.2 Carbon Monoxide + Hydrogen 44.5

Feed Stock #5

FS#5 68% paper; 32% Rubber AR MF Moisture 1.35 Ash 9.11 9.23 Volatile77.18 78.24 Fixed Carbon 12.36 12.53 S 0.23 0.01 H 5.84 5.92 C 45.9246.55 N 0.01 0.01 O 37.55 38.06 Cl 0.219 0.22 C/H 7.9 7.9 C/O 1.2 1.2HHV (BTU/lb) 9,250 9,377 HHV (BTU/lb), Calculated 8,288 Density (lb/cu.ft)

Feed Stock #5 Gasifier Output

Hydrogen, vol % 14.9 Nitrogen, vol % 51.6 Carbon Monoxide, vol % 17.0Methane, vol % 3.4 Carbon Dioxide, vol % 13.1 Hydrogen/Carbon Monoxide0.88 BTU/scf 140.56 Carbon Monoxide + Hydrogen 31.8

Feed Stock #6

FS#6 100% Rubber AR MF Moisture 0.06 Ash 6.12 6.12 Volatile 68.46 68.50Fixed Carbon 25.36 25.38 S 1.92 0.01 H 6.78 6.78 C 81.73 81.78 N 0.180.18 O 3.21 3.21 Cl C/H 12.1 12.1 C/O 25.5 25.5 HHV (BTU/lb) 15,78015,789 HHV (BTU/lb), Calculated 15,768 Density (lb/cu. ft) 28.6

Feed Stock #6 Gasifier Output

Hydrogen, vol % 8.65 Nitrogen, vol % 68.2 Carbon Monoxide, vol % 14.5Methane, vol % 0.71 Carbon Dioxide, vol % 6.9 Hydrogen/Carbon Monoxide0.60 BTU/scf 83.7 Carbon Monoxide + Hydrogen 23.2

Feed Stock #7

FS#7 80% Rubber, 20% Paper + 13% water AR MF Moisture 13.1 Ash 3.84 4.42Volatile 61.94 71.28 Fixed Carbon 21.12 24.30 S 1.28 0.01 H 5.87 6.75 C75.12 86.44 N 0.03 0.03 O 0.77 0.89 Cl 0.076 0.09 C/H 12.8 12.8 C/O 97.697.6 HHV (BTU/lb) 14,405 16,577 HHV (BTU/lb), Calculated 16,574 Density(lb/cu. ft)

Feed Stock #7 Gasifier Output

Hydrogen, vol % 28.6 Nitrogen, vol % 45.2 Carbon Monoxide, vol % 15.6Methane, vol % 2.7 Carbon Dioxide, vol % 7.9 Hydrogen/Carbon Monoxide1.83 BTU/scf 173.8 Carbon Monoxide + Hydrogen 44.2

Example 1

Test Method AS AIR DRY ASTM¹ # Parameter RECEIVED DRIED BASIS D 3302,Total Moisture, 21.04 — — 5142 % wt D 5142 Residual Moisture, — 7.04 — %wt D 5142 Ash, % wt 12.91 15.20 16.35 D 5142 Volatile, % wt 58.81 69.2474.49 Calculation Fixed Carbon, % wt 7.24 8.52 9.16 Total 100.00 100.00100.00 D 4239 Sulfur % 0.18 0.21 0.23 D 5865 HHV Btu/lb (Gross) 1089012821 13792 D 3176 Hydrogen, % wt 4.24 4.99 5.37 D 3176 Carbon, % wt33.84 39.84 42.86 D 3176 Nitrogen, % wt 0.24 0.29 0.31 Calculation %Oxygen by 27.55 32.42 34.88 difference ¹American Society for Testing andMaterials

Example 2

Test Method AS AIR DRY ASTM¹ # Parameter RECEIVED DRIED BASIS D 3302,Total Moisture, 13.26 — — 5142 % wt D 5142 Residual Moisture, — 6.09 — %wt D 5142 Ash, % wt 14.39 15.58 16.59 D 5142 Volatile, % wt 63.33 68.5773.02 Calculation Fixed Carbon, % wt 9.02 9.76 10.40 Total 100.00 100.00100.00 D 4239 Sulfur % 0.20 0.22 0.23 D 5865 HHV Btu/lb (Gross) 1116512088 12872 D 3176 Hydrogen, % wt 5.55 6.01 6.40 D 3176 Carbon, % wt41.68 45.12 48.05 D 3176 Nitrogen, % wt 0.21 0.23 0.24 Calculation %Oxygen by 24.71 26.75 28.49 difference ¹American Society for Testing andMaterials

Example 3

Test Method AS AIR DRY ASTM¹ # Parameter RECEIVED DRIED BASIS D 3302,Total Moisture, 15.06 — — 5142 % wt D 5142 Residual Moisture, — 4.16 — %wt D 5142 Ash, % wt 11.67 13.17 13.74 D 5142 Volatile, % wt 64.60 72.8976.05 Calculation Fixed Carbon, % wt 8.67 9.78 10.21 Total 100.00 100.00100.00 D 4239 Sulfur % 0.09 0.11 0.11 D 5865 HHV Btu/lb (Gross) 61886982 7285 D 3176 Hydrogen, % wt 4.93 5.56 5.80 D 3176 Carbon, % wt 34.9039.38 41.09 D 3176 Nitrogen, % wt 0.07 0.08 0.08 Calculation % Oxygen by33.28 37.55 39.18 difference D4208 Chlorine, % wt 0.75 0.84 0.88¹American Society for Testing and Materials

Example 4

Test Method AS AIR DRY ASTM¹ # Parameter RECEIVED DRIED BASIS D 3302,Total Moisture, % wt 14.99 — — 5142 D 5142 Residual Moisture, % wt —1.88 — D 5142 Ash, % wt 16.48 19.03 19.39 D 5142 Volatile, % wt 62.8472.53 73.92 Calculation Fixed Carbon, % wt 5.69 6.56 6.70 Total 100.00100.00 100.00 D 4239 Sulfur % 0.06 0.07 0.07 D 5865 HHV Btu/lb (Gross)6782 7828 7978 D 3176 Hydrogen, % wt 4.48 5.17 5.27 D 3176 Carbon, % wt31.94 36.96 37.57 D 3176 Nitrogen, % wt 0.08 0.09 0.09 Calculation %Oxygen by difference 31.97 36.80 37.61 D 4208 Chlorine, % wt 1.17 1.351.38

Example 5

Parameter Test Method Pellet Composition: 80% AS ASTM¹ # Fiber/20%plastic RECEIVED DRY BASIS E 939 Total Moisture, % wt 13.26 — E 830 Ash,% wt 5.24 6.04 E 897 Volatile, % wt 62.97 72.60 D 3172 Fixed Carbon, %wt 18.53 21.36 Total 100.00 100.00 D 4239 Sulfur % 0.15 0.17 E 711 HHVBtu/lb (Gross) 8806 10152 D 6373 Hydrogen, % wt 6.66 7.67 D 6373 Carbon,% wt 48.4 55.8 D 5373 Nitrogen, % wt 0.15 0.18 Calculation % Oxygen bydifference 26.14 30.14 D 4208 Chlorine, % wt 0.06 0.07 ¹American Societyfor Testing and Materials

Example 6

Parameter Test Method Pellet Composition: Plastics AS ASTM¹ # #2, and#4-7 RECEIVED DRY BASIS E 939 Total Moisture, % wt 2.1 — E 830 Ash, % wt7.82 7.98 E 897 Volatile, % wt 89.32 91.24 D 3172 Fixed Carbon, % wt0.76 0.78 Total 100.00 100.00 D 4239 Sulfur % 0.17 0.17 E 711 HHV Btu/lb(Gross) 17,192 17,560 D 6373 Hydrogen, % wt 13.57 13.86 D 6373 Carbon, %wt 78.85 80.54 D 5373 Nitrogen, % wt 0.01 0.01 D 4208 Chlorine, % wt0.33 0.34 ¹American Society for Testing and Materials

Example 7

Test Method Parameter AS ASTM¹ # Pellet Composition: Paper RECEIVED DRYBASIS E 939 Total Moisture, % wt 5.16 — E 830 Ash, % wt 41.79 44.06 E897 Volatile, % wt 48.27 50.90 D 3172 Fixed Carbon, % wt 4.78 5.04 Total100.00 100.00 D 4239 Sulfur % 0.17 0.18 E 711 HHV Btu/lb (Gross) 51465426 D 6373 Hydrogen, % wt 3.65 3.85 D 6373 Carbon, % wt 30.55 32.21 D5373 Nitrogen, % wt 0.43 0.45 Calculation % Oxygen by difference 18.2519.25 D 4208 Chlorine, % wt 0.47 0.50 ¹American Society for Testing andMaterials

Example 8

Parameter Test Method Pellet Composition: 10% AS ASTM¹ # Fiber/90%plastic RECEIVED DRY BASIS E 939 Total Moisture, % wt 2.53 — E 830 Ash,% wt 12.64 12.97 E 897 Volatile, % wt 83.50 85.67 D 3172 Fixed Carbon, %wt 1.33 1.36 D 4239 Sulfur % 0.17 0.17 E 711 HHV Btu/lb (Gross) 15,48215,885 D5373 Hydrogen, % wt 12.16 12.48 D5373 Carbon, % wt 71.99 73.86D5373 Nitrogen, % wt 0.07 0.07 Calculation % Oxygen by difference 0.440.45 D4208 Chlorine, % wt 0.35 0.36 ¹American Society for Testing andMaterials

While particular embodiments described herein have been illustrated anddescribed, it would be obvious to those skilled in the art that variousother changes and modifications can be made without departing from thespirit and scope of the disclosure. It is therefore intended to cover inthe appended claims all such changes and modifications that are withinthe scope of this invention.

1-76. (canceled)
 77. An engineered fuel feed stock, comprising at leastone component derived from a processed MSW waste stream, the feed stockcomprising: a carbon content of between about 70% and about 80%; asulfur content of less than about 0.5%; an O/C ratio between about 0.05and about 0.12, an H/C ratio between about 0.05 and about 0.07, andwherein the feed stock contains biodegradable waste andnon-biodegradable waste and substantially no glass, metals, grit, andnoncombustibles; and wherein the engineered fuel feed stock is in adensified form.
 78. The feed stock of claim 77, wherein the densifiedform is a cube.
 79. The feed stock of claim 77, wherein the densifiedform is a pellet.
 80. The feed stock of claim 77, wherein the densifiedform of the engineered fuel feed stock has a diameter of between about0.25 inches to about 1.5 inches.
 81. The feed stock of claim 77, whereinthe densified form of the engineered fuel feed stock has a length ofbetween about 0.5 inches to about 6 inches.
 82. The feed stock of claim77, wherein the densified form of the engineered fuel feed stock has asurface to volume ratio of between about 20:1 to about 3:1.
 83. The feedstock of claim 77, wherein the densified form of the engineered fuelfeed stock has a bulk density of about 10 lb/ft³ to about 75 lb/ft³. 84.The feed stock of claim 77, wherein the densified form of the engineeredfuel feed stock has a porosity of between about 0.2 and about 0.6. 85.The feed stock of claim 77, wherein the densified form of the engineeredfuel feed stock has an aspect ratio of between about 1 to about
 10. 86.The feed stock of claim 77, wherein the densified form of the engineeredfuel feed stock has a thermal conductivity of between about 0.023BTU/(ft·hr·° F.) and about 0.578 BTU/(ft·hr·° F.).
 87. The feed stock ofclaim 77, wherein the densified form of the engineered fuel feed stockhas a specific heat capacity of between about 4.78×10⁻⁵ BTU/(lb·° F.) to4.78×10⁻⁴ BTU/(lb·° F.).
 88. The feed stock of claim 77, wherein thedensified form of the engineered fuel feed stock has a thermaldiffusivity of between about 1.08×10-5 ft2/s to 2.16×10-5 ft2/s.
 89. Thefeed stock of claim 77, wherein the feed stock has a HHV of betweenabout 7,000 BTU/lb and about 11,000 BTU/lb.